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# big-o-performance A simple html app to demonstrate performance costs of data structures. - Clone the project - Navigate to the root of the project in a termina or command prompt - Run 'npm install' - Run 'npm start' - Go to the URL specified in the terminal or command prompt to try out the app. # This app was created from the Create React App NPM. Below are instructions from that project. Below you will find some information on how to perform common tasks. You can find the most recent version of this guide [here](https://github.com/facebookincubator/create-react-app/blob/master/template/README.md). ## Table of Contents - [Updating to New Releases](#updating-to-new-releases) - [Sending Feedback](#sending-feedback) - [Folder Structure](#folder-structure) - [Available Scripts](#available-scripts) - [npm start](#npm-start) - [npm run build](#npm-run-build) - [npm run eject](#npm-run-eject) - [Displaying Lint Output in the Editor](#displaying-lint-output-in-the-editor) - [Installing a Dependency](#installing-a-dependency) - [Importing a Component](#importing-a-component) - [Adding a Stylesheet](#adding-a-stylesheet) - [Post-Processing CSS](#post-processing-css) - [Adding Images and Fonts](#adding-images-and-fonts) - [Adding Bootstrap](#adding-bootstrap) - [Adding Flow](#adding-flow) - [Adding Custom Environment Variables](#adding-custom-environment-variables) - [Integrating with a Node Backend](#integrating-with-a-node-backend) - [Proxying API Requests in Development](#proxying-api-requests-in-development) - [Deployment](#deployment) - [Now](#now) - [Heroku](#heroku) - [Surge](#surge) - [GitHub Pages](#github-pages) - [Something Missing?](#something-missing) ## Updating to New Releases Create React App is divided into two packages: * `create-react-app` is a global command-line utility that you use to create new projects. * `react-scripts` is a development dependency in the generated projects (including this one). You almost never need to update `create-react-app` itself: it’s delegates all the setup to `react-scripts`. When you run `create-react-app`, it always creates the project with the latest version of `react-scripts` so you’ll get all the new features and improvements in newly created apps automatically. To update an existing project to a new version of `react-scripts`, [open the changelog](https://github.com/facebookincubator/create-react-app/blob/master/CHANGELOG.md), find the version you’re currently on (check `package.json` in this folder if you’re not sure), and apply the migration instructions for the newer versions. In most cases bumping the `react-scripts` version in `package.json` and running `npm install` in this folder should be enough, but it’s good to consult the [changelog](https://github.com/facebookincubator/create-react-app/blob/master/CHANGELOG.md) for potential breaking changes. We commit to keeping the breaking changes minimal so you can upgrade `react-scripts` painlessly. ## Sending Feedback We are always open to [your feedback](https://github.com/facebookincubator/create-react-app/issues). ## Folder Structure After creation, your project should look like this: ``` my-app/ README.md index.html favicon.ico node_modules/ package.json src/ App.css App.js index.css index.js logo.svg ``` For the project to build, **these files must exist with exact filenames**: * `index.html` is the page template; * `favicon.ico` is the icon you see in the browser tab; * `src/index.js` is the JavaScript entry point. You can delete or rename the other files. You may create subdirectories inside `src`. For faster rebuilds, only files inside `src` are processed by Webpack. You need to **put any JS and CSS files inside `src`**, or Webpack won’t see them. You can, however, create more top-level directories. They will not be included in the production build so you can use them for things like documentation. ## Available Scripts In the project directory, you can run: ### `npm start` Runs the app in the development mode.<br> Open [http://localhost:3000](http://localhost:3000) to view it in the browser. The page will reload if you make edits.<br> You will also see any lint errors in the console. ### `npm run build` Builds the app for production to the `build` folder.<br> It correctly bundles React in production mode and optimizes the build for the best performance. The build is minified and the filenames include the hashes.<br> Your app is ready to be deployed! ### `npm run eject` **Note: this is a one-way operation. Once you `eject`, you can’t go back!** If you aren’t satisfied with the build tool and configuration choices, you can `eject` at any time. This command will remove the single build dependency from your project. Instead, it will copy all the configuration files and the transitive dependencies (Webpack, Babel, ESLint, etc) right into your project so you have full control over them. All of the commands except `eject` will still work, but they will point to the copied scripts so you can tweak them. At this point you’re on your own. You don’t have to ever use `eject`. The curated feature set is suitable for small and middle deployments, and you shouldn’t feel obligated to use this feature. However we understand that this tool wouldn’t be useful if you couldn’t customize it when you are ready for it. ## Displaying Lint Output in the Editor >Note: this feature is available with `react-scripts@0.2.0` and higher. Some editors, including Sublime Text, Atom, and Visual Studio Code, provide plugins for ESLint. They are not required for linting. You should see the linter output right in your terminal as well as the browser console. However, if you prefer the lint results to appear right in your editor, there are some extra steps you can do. You would need to install an ESLint plugin for your editor first. >**A note for Atom `linter-eslint` users** >If you are using the Atom `linter-eslint` plugin, make sure that **Use global ESLint installation** option is checked: ><img src="http://i.imgur.com/yVNNHJM.png" width="300"> Then make sure `package.json` of your project ends with this block: ```js { // ... "eslintConfig": { "extends": "./node_modules/react-scripts/config/eslint.js" } } ``` Projects generated with `react-scripts@0.2.0` and higher should already have it. If you don’t need ESLint integration with your editor, you can safely delete those three lines from your `package.json`. Finally, you will need to install some packages *globally*: ```sh npm install -g eslint babel-eslint eslint-plugin-react eslint-plugin-import eslint-plugin-jsx-a11y eslint-plugin-flowtype ``` We recognize that this is suboptimal, but it is currently required due to the way we hide the ESLint dependency. The ESLint team is already [working on a solution to this](https://github.com/eslint/eslint/issues/3458) so this may become unnecessary in a couple of months. ## Installing a Dependency The generated project includes React and ReactDOM as dependencies. It also includes a set of scripts used by Create React App as a development dependency. You may install other dependencies (for example, React Router) with `npm`: ``` npm install --save <library-name> ``` ## Importing a Component This project setup supports ES6 modules thanks to Babel. While you can still use `require()` and `module.exports`, we encourage you to use [`import` and `export`](http://exploringjs.com/es6/ch_modules.html) instead. For example: ### `Button.js` ```js import React, { Component } from 'react'; class Button extends Component { render() { // ... } } export default Button; // Don’t forget to use export default! ``` ### `DangerButton.js` ```js import React, { Component } from 'react'; import Button from './Button'; // Import a component from another file class DangerButton extends Component { render() { return <Button color="red" />; } } export default DangerButton; ``` Be aware of the [difference between default and named exports](http://stackoverflow.com/questions/36795819/react-native-es-6-when-should-i-use-curly-braces-for-import/36796281#36796281). It is a common source of mistakes. We suggest that you stick to using default imports and exports when a module only exports a single thing (for example, a component). That’s what you get when you use `export default Button` and `import Button from './Button'`. Named exports are useful for utility modules that export several functions. A module may have at most one default export and as many named exports as you like. Learn more about ES6 modules: * [When to use the curly braces?](http://stackoverflow.com/questions/36795819/react-native-es-6-when-should-i-use-curly-braces-for-import/36796281#36796281) * [Exploring ES6: Modules](http://exploringjs.com/es6/ch_modules.html) * [Understanding ES6: Modules](https://leanpub.com/understandinges6/read#leanpub-auto-encapsulating-code-with-modules) ## Adding a Stylesheet This project setup uses [Webpack](https://webpack.github.io/) for handling all assets. Webpack offers a custom way of “extending” the concept of `import` beyond JavaScript. To express that a JavaScript file depends on a CSS file, you need to **import the CSS from the JavaScript file**: ### `Button.css` ```css .Button { padding: 20px; } ``` ### `Button.js` ```js import React, { Component } from 'react'; import './Button.css'; // Tell Webpack that Button.js uses these styles class Button extends Component { render() { // You can use them as regular CSS styles return <div className="Button" />; } } ``` **This is not required for React** but many people find this feature convenient. You can read about the benefits of this approach [here](https://medium.com/seek-ui-engineering/block-element-modifying-your-javascript-components-d7f99fcab52b). However you should be aware that this makes your code less portable to other build tools and environments than Webpack. In development, expressing dependencies this way allows your styles to be reloaded on the fly as you edit them. In production, all CSS files will be concatenated into a single minified `.css` file in the build output. If you are concerned about using Webpack-specific semantics, you can put all your CSS right into `src/index.css`. It would still be imported from `src/index.js`, but you could always remove that import if you later migrate to a different build tool. ## Post-Processing CSS This project setup minifies your CSS and adds vendor prefixes to it automatically through [Autoprefixer](https://github.com/postcss/autoprefixer) so you don’t need to worry about it. For example, this: ```css .App { display: flex; flex-direction: row; align-items: center; } ``` becomes this: ```css .App { display: -webkit-box; display: -ms-flexbox; display: flex; -webkit-box-orient: horizontal; -webkit-box-direction: normal; -ms-flex-direction: row; flex-direction: row; -webkit-box-align: center; -ms-flex-align: center; align-items: center; } ``` There is currently no support for preprocessors such as Less, or for sharing variables across CSS files. ## Adding Images and Fonts With Webpack, using static assets like images and fonts works similarly to CSS. You can **`import` an image right in a JavaScript module**. This tells Webpack to include that image in the bundle. Unlike CSS imports, importing an image or a font gives you a string value. This value is the final image path you can reference in your code. Here is an example: ```js import React from 'react'; import logo from './logo.png'; // Tell Webpack this JS file uses this image console.log(logo); // /logo.84287d09.png function Header() { // Import result is the URL of your image return <img src={logo} alt="Logo" />; } export default function Header; ``` This works in CSS too: ```css .Logo { background-image: url(./logo.png); } ``` Webpack finds all relative module references in CSS (they start with `./`) and replaces them with the final paths from the compiled bundle. If you make a typo or accidentally delete an important file, you will see a compilation error, just like when you import a non-existent JavaScript module. The final filenames in the compiled bundle are generated by Webpack from content hashes. If the file content changes in the future, Webpack will give it a different name in production so you don’t need to worry about long-term caching of assets. Please be advised that this is also a custom feature of Webpack. **It is not required for React** but many people enjoy it (and React Native uses a similar mechanism for images). However it may not be portable to some other environments, such as Node.js and Browserify. If you prefer to reference static assets in a more traditional way outside the module system, please let us know [in this issue](https://github.com/facebookincubator/create-react-app/issues/28), and we will consider support for this. ## Adding Bootstrap You don’t have to use [React Bootstrap](https://react-bootstrap.github.io) together with React but it is a popular library for integrating Bootstrap with React apps. If you need it, you can integrate it with Create React App by following these steps: Install React Bootstrap and Bootstrap from NPM. React Bootstrap does not include Bootstrap CSS so this needs to be installed as well: ``` npm install react-bootstrap --save npm install bootstrap@3 --save ``` Import Bootstrap CSS and optionally Bootstrap theme CSS in the ```src/index.js``` file: ```js import 'bootstrap/dist/css/bootstrap.css'; import 'bootstrap/dist/css/bootstrap-theme.css'; ``` Import required React Bootstrap components within ```src/App.js``` file or your custom component files: ```js import { Navbar, Jumbotron, Button } from 'react-bootstrap'; ``` Now you are ready to use the imported React Bootstrap components within your component hierarchy defined in the render method. Here is an example [`App.js`](https://gist.githubusercontent.com/gaearon/85d8c067f6af1e56277c82d19fd4da7b/raw/6158dd991b67284e9fc8d70b9d973efe87659d72/App.js) redone using React Bootstrap. ## Adding Flow Flow typing is currently [not supported out of the box](https://github.com/facebookincubator/create-react-app/issues/72) with the default `.flowconfig` generated by Flow. If you run it, you might get errors like this: ```js node_modules/fbjs/lib/Deferred.js.flow:60 60: Promise.prototype.done.apply(this._promise, arguments); ^^^^ property `done`. Property not found in 495: declare class Promise<+R> { ^ Promise. See lib: /private/tmp/flow/flowlib_34952d31/core.js:495 node_modules/fbjs/lib/shallowEqual.js.flow:29 29: return x !== 0 || 1 / (x: $FlowIssue) === 1 / (y: $FlowIssue); ^^^^^^^^^^ identifier `$FlowIssue`. Could not resolve name src/App.js:3 3: import logo from './logo.svg'; ^^^^^^^^^^^^ ./logo.svg. Required module not found src/App.js:4 4: import './App.css'; ^^^^^^^^^^^ ./App.css. Required module not found src/index.js:5 5: import './index.css'; ^^^^^^^^^^^^^ ./index.css. Required module not found ``` To fix this, change your `.flowconfig` to look like this: ```ini [libs] ./node_modules/fbjs/flow/lib [options] esproposal.class_static_fields=enable esproposal.class_instance_fields=enable module.name_mapper='^\(.*\)\.css$' -> 'react-scripts/config/flow/css' module.name_mapper='^\(.*\)\.\(jpg\|png\|gif\|eot\|otf\|webp\|svg\|ttf\|woff\|woff2\|mp4\|webm\)$' -> 'react-scripts/config/flow/file' suppress_type=$FlowIssue suppress_type=$FlowFixMe ``` Re-run flow, and you shouldn’t get any extra issues. If you later `eject`, you’ll need to replace `react-scripts` references with the `<PROJECT_ROOT>` placeholder, for example: ```ini module.name_mapper='^\(.*\)\.css$' -> '<PROJECT_ROOT>/config/flow/css' module.name_mapper='^\(.*\)\.\(jpg\|png\|gif\|eot\|otf\|webp\|svg\|ttf\|woff\|woff2\|mp4\|webm\)$' -> '<PROJECT_ROOT>/config/flow/file' ``` We will consider integrating more tightly with Flow in the future so that you don’t have to do this. ## Adding Custom Environment Variables >Note: this feature is available with `react-scripts@0.2.3` and higher. Your project can consume variables declared in your environment as if they were declared locally in your JS files. By default you will have `NODE_ENV` defined for you, and any other environment variables starting with `REACT_APP_`. These environment variables will be defined for you on `process.env`. For example, having an environment variable named `REACT_APP_SECRET_CODE` will be exposed in your JS as `process.env.REACT_APP_SECRET_CODE`, in addition to `process.env.NODE_ENV`. These environment variables can be useful for displaying information conditionally based on where the project is deployed or consuming sensitive data that lives outside of version control. First, you need to have environment variables defined, which can vary between OSes. For example, let's say you wanted to consume a secret defined in the environment inside a `<form>`: ```jsx render() { return ( <div> <small>You are running this application in <b>{process.env.NODE_ENV}</b> mode.</small> <form> <input type="hidden" defaultValue={process.env.REACT_APP_SECRET_CODE} /> </form> </div> ); } ``` The above form is looking for a variable called `REACT_APP_SECRET_CODE` from the environment. In order to consume this value, we need to have it defined in the environment: ### Windows (cmd.exe) ```cmd set REACT_APP_SECRET_CODE=abcdef&&npm start ``` (Note: the lack of whitespace is intentional.) ### Linux, OS X (Bash) ```bash REACT_APP_SECRET_CODE=abcdef npm start ``` > Note: Defining environment variables in this manner is temporary for the life of the shell session. Setting permanent environment variables is outside the scope of these docs. With our environment variable defined, we start the app and consume the values. Remember that the `NODE_ENV` variable will be set for you automatically. When you load the app in the browser and inspect the `<input>`, you will see its value set to `abcdef`, and the bold text will show the environment provided when using `npm start`: ```html <div> <small>You are running this application in <b>development</b> mode.</small> <form> <input type="hidden" value="abcdef" /> </form> </div> ``` Having access to the `NODE_ENV` is also useful for performing actions conditionally: ```js if (process.env.NODE_ENV !== 'production') { analytics.disable(); } ``` ## Integrating with a Node Backend Check out [this tutorial](https://www.fullstackreact.com/articles/using-create-react-app-with-a-server/) for instructions on integrating an app with a Node backend running on another port, and using `fetch()` to access it. You can find the companion GitHub repository [here](https://github.com/fullstackreact/food-lookup-demo). ## Proxying API Requests in Development >Note: this feature is available with `react-scripts@0.2.3` and higher. People often serve the front-end React app from the same host and port as their backend implementation. For example, a production setup might look like this after the app is deployed: ``` / - static server returns index.html with React app /todos - static server returns index.html with React app /api/todos - server handles any /api/* requests using the backend implementation ``` Such setup is **not** required. However, if you **do** have a setup like this, it is convenient to write requests like `fetch('/api/todos')` without worrying about redirecting them to another host or port during development. To tell the development server to proxy any unknown requests to your API server in development, add a `proxy` field to your `package.json`, for example: ```js "proxy": "http://localhost:4000", ``` This way, when you `fetch('/api/todos')` in development, the development server will recognize that it’s not a static asset, and will proxy your request to `http://localhost:4000/api/todos` as a fallback. Conveniently, this avoids [CORS issues](http://stackoverflow.com/questions/21854516/understanding-ajax-cors-and-security-considerations) and error messages like this in development: ``` Fetch API cannot load http://localhost:4000/api/todos. No 'Access-Control-Allow-Origin' header is present on the requested resource. Origin 'http://localhost:3000' is therefore not allowed access. If an opaque response serves your needs, set the request's mode to 'no-cors' to fetch the resource with CORS disabled. ``` Keep in mind that `proxy` only has effect in development (with `npm start`), and it is up to you to ensure that URLs like `/api/todos` point to the right thing in production. You don’t have to use the `/api` prefix. Any unrecognized request will be redirected to the specified `proxy`. Currently the `proxy` option only handles HTTP requests, and it won’t proxy WebSocket connections. If the `proxy` option is **not** flexible enough for you, alternatively you can: * Enable CORS on your server ([here’s how to do it for Express](http://enable-cors.org/server_expressjs.html)). * Use [environment variables](#adding-custom-environment-variables) to inject the right server host and port into your app. ## Deployment By default, Create React App produces a build assuming your app is hosted at the server root. To override this, specify the `homepage` in your `package.json`, for example: ```js "homepage": "http://mywebsite.com/relativepath", ``` This will let Create React App correctly infer the root path to use in the generated HTML file. ### Now See [this example](https://github.com/xkawi/create-react-app-now) for a zero-configuration single-command deployment with [now](https://zeit.co/now). ### Heroku Use the [Heroku Buildpack for Create React App](https://github.com/mars/create-react-app-buildpack). You can find instructions in [Deploying React with Zero Configuration](https://blog.heroku.com/deploying-react-with-zero-configuration). ### Surge Install the Surge CLI if you haven't already by running `npm install -g surge`. Run the `surge` command and log in you or create a new account. You just need to specify the *build* folder and your custom domain, and you are done. ```sh email: email@domain.com password: ******** project path: /path/to/project/build size: 7 files, 1.8 MB domain: create-react-app.surge.sh upload: [====================] 100%, eta: 0.0s propagate on CDN: [====================] 100% plan: Free users: email@domain.com IP Address: X.X.X.X Success! Project is published and running at create-react-app.surge.sh ``` Note that in order to support routers that use html5 `pushState` API, you may want to rename the `index.html` in your build folder to `200.html` before deploying to Surge. This [ensures that every URL falls back to that file](https://surge.sh/help/adding-a-200-page-for-client-side-routing). ### GitHub Pages >Note: this feature is available with `react-scripts@0.2.0` and higher. Open your `package.json` and add a `homepage` field: ```js "homepage": "http://myusername.github.io/my-app", ``` **The above step is important!** Create React App uses the `homepage` field to determine the root URL in the built HTML file. Now, whenever you run `npm run build`, you will see a cheat sheet with a sequence of commands to deploy to GitHub pages: ```sh git commit -am "Save local changes" git checkout -B gh-pages git add -f build git commit -am "Rebuild website" git filter-branch -f --prune-empty --subdirectory-filter build git push -f origin gh-pages git checkout - ``` You may copy and paste them, or put them into a custom shell script. You may also customize them for another hosting provider. Note that GitHub Pages doesn't support routers that use the HTML5 `pushState` history API under the hood (for example, React Router using `browserHistory`). This is because when there is a fresh page load for a url like `http://user.github.io/todomvc/todos/42`, where `/todos/42` is a frontend route, the GitHub Pages server returns 404 because it knows nothing of `/todos/42`. If you want to add a router to a project hosted on GitHub Pages, here are a couple of solutions: * You could switch from using HTML5 history API to routing with hashes. If you use React Router, you can switch to `hashHistory` for this effect, but the URL will be longer and more verbose (for example, `http://user.github.io/todomvc/#/todos/42?_k=yknaj`). [Read more](https://github.com/reactjs/react-router/blob/master/docs/guides/Histories.md#histories) about different history implementations in React Router. * Alternatively, you can use a trick to teach GitHub Pages to handle 404 by redirecting to your `index.html` page with a special redirect parameter. You would need to add a `404.html` file with the redirection code to the `build` folder before deploying your project, and you’ll need to add code handling the redirect parameter to `index.html`. You can find a detailed explanation of this technique [in this guide](https://github.com/rafrex/spa-github-pages). ## Something Missing? If you have ideas for more “How To” recipes that should be on this page, [let us know](https://github.com/facebookincubator/create-react-app/issues) or [contribute some!](https://github.com/facebookincubator/create-react-app/edit/master/template/README.md)

What is JavaScript and what does it do? Before you start learning something new, it’s important to understand exactly what it is and what it does. This is especially useful when it comes to mastering a new programming language. In simple terms, JavaScript is a programming language used to make websites interactive. If you think about the basic makeup of a website, you have HTML, which describes and defines the basic content and structure of the website, then you have CSS, which tells the browser how this HTML content should be displayed—determining things like color and font. With just HTML and CSS, you have a website that looks good but doesn’t actually do much. JavaScript brings the website to life by adding functionality. JavaScript is responsible for elements that the user can interact with, such as drop-down menus, modal windows, and contact forms. It is also used to create things like animations, video players, and interactive maps. Nowadays, JavaScript is an all-purpose programming language—meaning it runs across the entire software stack. The most popular application of JavaScript is on the client side (aka frontend), but since Node.js came on the scene, many people run JavaScript on the server side (aka backend) as well. When used on the client side, JavaScript code is read, interpreted, and executed in the user’s web browser. When used on the server side, it is run on a remote computer. You can learn more about the difference between frontend and backend programming here. JavaScript isn’t only used to create websites. It can also be used to build browser-based games and, with the help of certain frameworks, mobile apps for different operating systems. The creation of new libraries and frameworks is also making it possible to build backend programs with JavaScript, such as web apps and server apps. Is it still worth learning JavaScript in 2021? The world of web development is constantly moving. With so many new tools popping up all the time, it can be extremely difficult to know where you should focus your efforts. As an aspiring developer, you’ll want to make sure that what you’re learning is still relevant in today’s industry. If you’re having doubts about JavaScript, it’s important to know that, since its creation in 1995, JavaScript is pretty much everywhere on the web—and that’s not likely to change any time soon. According to the 2020 StackOverflow developer survey, JavaScript is the most commonly used programming language for the eighth year in a row. It is currently used by 94.5% of all websites and, despite originally being designed as a client-side language, JavaScript has now made its way to the server-side of websites (thanks to Node.js), mobile devices (thanks to React Native and Ionic) and desktop (courtesy of Electron). As long as people are interacting with the web, you can assume that JavaScript is highly relevant—there’s no doubt that this is a language worth knowing! With that in mind, let’s look at some of the key benefits of becoming a JavaScript expert. Why learn JavaScript? The most obvious reason for learning JavaScript is if you have hopes of becoming a web developer. Even if you haven’t got your heart set on a tech career, being proficient in JavaScript will enable you to build websites from scratch—a pretty useful skill to have in today’s job market! If you do want to become a web developer, here are some of the main reasons why you should learn JavaScript: JavaScript experts are versatile JavaScript is an extremely versatile language. Once you’ve mastered it, the possibilities are endless: you can code on the client-side (frontend) using Angular and on the server-side (backend) using Node.js. You can also develop web, mobile, and desktop apps using React, React Native, and Electron, and you can even get involved in machine learning. If you want to become a frontend developer, JavaScript is a prerequisite. However, that’s not the only career path open to you as a JavaScript expert. Mastering this key programming language could see you go on to work in full-stack development, games development, information security software engineering, machine learning, and artificial intelligence—to name just a few! Ultimately, if you want any kind of development or engineering career, proficiency in JavaScript is a must. JavaScript experts are in-demand (and well-paid) JavaScript is the most popular programming language in the world, so it’s no wonder that JavaScript is one of the most sought-after skills in the web development industry today. According to the Devskiller IT Skills and Hiring Report 2020, 72% of companies are looking to hire JavaScript experts. Enter the search term “JavaScript” on job site Indeed and you’ll find over 40,000 jobs requiring this skill (in the US). Run the same search on LinkedIn and the results are in excess of 125,000. At the same time, the global demand for JavaScript seems to outweigh the expertise available on the market. According to this 2018 HackerRank report, 48% of employers worldwide need developers with JavaScript skills, while only 42% of student developers claim to be proficient in JavaScript. And, in their most recent report for 2020, HackerRank once again reports that JavaScript is the most popular language that hiring mangers look for in a web developer candidate. Not only are JavaScript experts in demand—they are also well-paid. In the United States, JavaScript developers earn an average yearly salary of $111,953 per year. We’ve covered this topic in more detail in our JavaScript salary guide, but as you can see, learning JavaScript can really boost your earning potential as a developer. JavaScript is beginner-friendly Compared to many other programming languages, JavaScript offers one of the more beginner-friendly entry points into the world of coding. The great thing about JavaScript is that it comes installed on every modern web browser—there’s no need to set up any kind of development environment, which means you can start coding with JavaScript right away! Another advantage of learning JavaScript as your first programming language is that you get instant feedback; with a minimal amount of JavaScript code, you’ll immediately see visible results. There’s also a huge JavaScript community on sites like Stack Overflow, so you’ll find plenty of support as you learn. Not only is JavaScript beginner-friendly; it will also set you up with some extremely valuable transferable skills. JavaScript supports object-oriented, functional, and imperative styles of programming—skills which can be transferred to any new language you might learn later on, such as Python, Java, or C++. JavaScript provides a crucial introduction to key principles and practices that you’ll take with you throughout your career as a developer. Should you learn plain JavaScript first or can you skip to frameworks and libraries? When deciding whether or not to learn JavaScript, what you’re really asking is whether or not you should learn “vanilla” JavaScript. Vanilla JavaScript just means plain JavaScript without any libraries or frameworks. Let’s explore what this means in more detail now. What is meant by vanilla JavaScript, libraries, and frameworks? If you research the term “vanilla JavaScript”, you might run into some confusion; however, all you need to know is that vanilla JavaScript is used to refer to native, standards-based, non-extended JavaScript. There is no difference between vanilla JavaScript and JavaScript—it’s just there to emphasize the usage of plain JavaScript without the use of libraries and frameworks. So what are libraries and frameworks? JavaScript libraries and frameworks both contain sets of prewritten, ready-to-use JavaScript code—but they’re not the same thing. You can think of a framework as your blueprint for building a website: it gives you a structure to work from, and contains ready-made components and tools that help you to build certain elements much quicker than if you were to code them from scratch. Some popular JavaScript frameworks include Angular, React, Vue, and Node.js. Frameworks also contain libraries. Libraries are smaller than frameworks, and tend to be used for more specific cases. A JavaScript library contains sets of JavaScript code which can be called upon to implement certain functions and features. Let’s imagine you want to code a particular element into your website. You could write, say, ten lines of JavaScript from scratch—or you could take the condensed, ready-made version from your chosen JavaScript library. Some examples of JavaScript libraries include jQuery, Lodash, and Underscore. The easiest way to understand how frameworks and libraries work together is to imagine you are building a house. The framework provides the foundation and the structure, while the library enables you to add in ready-made components (like furniture) rather than building your own from scratch. You can learn more about the relationship between languages and libraries in this post explaining the main differences between JavaScript and jQuery. For now, let’s go back to our original question: How important is it to learn vanilla JavaScript? Should you learn vanilla JavaScript first? When it comes to learning JavaScript, it can be tempting to skip ahead to those time-saving frameworks and libraries we just talked about—and many developers do. However, there are many compelling arguments for learning plain JavaScript first. While JavaScript frameworks may help you get the job done quicker, there’s only so far you can go if you don’t understand the core concepts behind these frameworks. Frontend developer Abhishek Nagekar describes how not learning vanilla JavaScript came back to bite him when he started learning the JavaScript frameworks Node and Express: “As I went to write more and more code in Node and Express, I began to get stuck at even the tiniest problems. Suddenly, I was surrounded with words like callbacks, closures, event loop and prototype. It felt like I got a reintroduction to JavaScript, but this time, it was not a toddler playing in its cradle, it was something of a mysterious monster, challenging me on every other step for not having taken it seriously.” The above Tweet references a long-running joke within the developer community, and although it dates way back to 2015, it’s still highly relevant today. If you want to become a developer who can innovate, not just execute, you need to understand the underlying principles of the web—not just the shortcuts. This means learning vanilla JavaScript before you move on to frameworks. In fact, understanding plain JavaScript will help you later on when it comes to deciding whether to use a framework for a certain project, and if so, which framework to use. Why Study JavaScript? JavaScript is one of the 3 languages all web developers must learn: 1. HTML to define the content of web pages 2. CSS to specify the layout of web pages 3. JavaScript to program the behavior of web pages Learning Speed In this tutorial, the learning speed is your choice. Everything is up to you. If you are struggling, take a break, or re-read the material. Always make sure you understand all the "Try-it-Yourself" examples. The only way to become a clever programmer is to: Practice. Practice. Practice. Code. Code. Code ! Commonly Asked Questions How do I get JavaScript? Where can I download JavaScript? Is JavaScript Free? You don't have to get or download JavaScript. JavaScript is already running in your browser on your computer, on your tablet, and on your smart-phone. JavaScript is free to use for everyone.

Please Read Me First. This is a set of java file of my final version of electronic artifacts. This is a game to map my experience in Disney World, in Orlando during this spring break. However, because of my limited skills in computer science, I really have no idea how to simplify the process to run the game. Sorry for the inconvenience. In order to run the game, you may need to install JAVA. I hope the following links will help you.     http://www.oracle.com/technetwork/java/javase/downloads/index-jsp-138363.html#javasejdk
    http://www.cc.gatech.edu/~simpkins/teaching/gatech/cs1331/guides/install-java.html My main file is called Disney. You can call Disney in console to start the game. However, I failed to putting all the things inside Disney file. Therefore, you may also need to call AdventureLand, MainStreet, and FrontierLand to start other three games. I hope this will help you. Sorry again for the inconvenience. 1. the structure of my project My project only focused on my trip in Magic Kingdom, one part of Disney world in Orlando. It is a game which guides players to choose from six sub-games, which match six sections of the park, Main Street U.S.A, Tomorrowland, Adventureland, Frontierland, Fantasyland and Liberty Square. I chose one of the rides I took in each section which, from my perspective, shows what I found interesting in Disney world. I changed what I experienced in the park into a small computer game. I want to share my experience with others while they play my games. In the following part of self reflection, I explain the background, rules and other things about each game. For convenience of matching them, I use different color to mark different parts. I hope it will help readers a little bit when they are lost in my disordered reflections. 1. the hall of presidents - Liberty Square 2. Festivall parade - Fantasyland (I explain this one in the part of technology skill limitations) 3. Big Thunder Mountain Railroad - Frontierland 4.talking with Woody- Adventureland 5. Stitch Store - Tomorrowland 6. lunch time - Main Street USA 3. my reflection of the trip in Disney World from dream to reality When I exited Disney resort, I found a sign along the street welcomed people back to real world. Actually, when I was in Orlando, I couldn't believe as an adult, people can mess up fantasy world in the theme parks and the real world. Nevertheless, I felt I was still in fantasy world, when I dreamed twice that I fought for the key to open the door of future. As is known to all, while sleeping, people always dream about what people thinks in the daytime. Therefore, my dream shows that my mind still stayed in the world with Mickey and Donald. I believe that it is experiencing fantasy world which is the source of the greatest happiness people get from theme park. On the one hand, everybody has pressure in real life especially for adults. They can get out of pressure for a day trip in theme park. They can experience different lives here with cartoon characters. On the other hand, sometimes, it is a really hard task to fulfill some dreams, such as being a princess. However, in Disney world, you can dress up the same as Snow White, waiting for your prince; you can go to space by rocket; you can also travel all over the world in one day and enjoy the food of each country. These are all the magic of theme parks. Therefore, in my game, I learnt the way which Disney design their rides to focus on the background story of the game instead of the game itself. For example, there is a ride called Big Thunder Mountain Railroad, which streaks through a haunted gold-mining town aboard a rollicking runaway mine train. The views around the ride were like a gold mining town. There were tools for gold-mining around the railroad and the railroad looked like very old. In order to show riders that it was a haunted gold-mining town, the train always took a sudden turn or speed up quickly to scare people. I decided to name one of my game, which was inspired by this ride, the same name, Big Thunder Mountain Railroad. Instead of sitting inside the mine train to travel around the haunted town, mine was for users to use keyboard to control the train to travel around the gridding railroad. I place traps inside several parts of gridding to "scare" players, who cannot know where traps are until they get into them. If I know how to use animation, I will show scary pictures when players drive their train to the traps. Unlike the ride in Disney, my players can no longer travel once they encounter a trap because their train may have some problems to keep moving. Also, the main goal in the game is to find the gold. However, as we know, finding gold is really hard. Therefore, players must go to find Aladdin's Wonderful lamp where also places inside the gridding while players cannot see its exact place until they happen to drive inside the part where lamp is. Aladdin's Wonderful lamp will show players the map of the gold and when people get to the gold mine, they win. However, there is another limitation of the game. Haunted town is so dangerous during the night. Therefore, players only have 12 hours to finish the task. Train can drive one square in 20 min. Therefore, train can only move 36 times or they will also be caught by traps. In this game, I want to show audiences I have a background story like rides in Disney World. Players need to find the gold in a haunted gold-mining town. Also, in order to show the relationship with Disney, I use Aladdin's Wonderful Lamp as the guide for the players, which is a well known characters in Disney cartoon. I created another game, called talking with Woody to show the magic power of Disney characters. There are a lot of chances to meet Disney characters in Disney world. On the one hand, travelers, especially small kids, are really excited to meet the characters they watched on TV. I think some kids may believe they take pictures with real Mickey Mouse. On the hand, staffs in Disney who wear the costumes are really tired. It was hot in Orlando last week, but all costumes were very heavy. I was moved by the staffs inside Mickey. They also need to mimic the actions of characters and also need to show kindness and warmness to children. It seems like a really hard job. Therefore, I decide to show this part of Disney in my project as well. I decided to use Woody, a toy all the toys look up to. He is smart, kind and brave like a cowboy should be. He is more than a top, he is friend to everyone enjoying the movie Toy. In order to create an interactive game, I planned to ask players to guide Woody. Players need to call Woody before their instructions. For instance, if players say (actually players are typing) "Woody, please sit down", Woody will sit down (actually, there will be another line on the screen showing the same as players import). However, if players are rude and just say "sit down" without calling Woody, Woody won't act (actually there is just nothing showing up on the screen). great facilities to provide convenience to everyone The facilities to satisfy needs for special groups of people, like small kids or disabled people, are well developed. In the past in China, it seemed impossible for parents to take infants and small kids to travel. The road is not flat or wide enough for strollers or wheelchairs. However, in Disney world, everything seemed like well prepared for everyone to use. There are strollers rentals, and electric conveyance vehicles rentals, which are available to rent throughout Disney world. There are baby care center for mothers to feed, change and nurse little ones. There are locker rentals for storing personal items. There are also hearing disability services which have sign language interpretation to help disabled people to enjoy fantasy world. There are still a lot other convenient services in Disney world. I think the purpose of these services show the pursue of equality among everyone in the world. On the one hand, I am really touched by the availability of these services here. It seems Disney try its best to service everyone who have desire to experience fantasy land. On the other hand, in this way, Disney can attract more travelers in order to make more money in some ways. Also, in Disney, it seems like a tradition that there are stores at the exit of the famous rides. Somebody may think it is just a strategy to make people shopping a lot. However, I think it also provides some convenience that travelers can buy souvenirs where is memorable. For example, when I finished my trip in Escape Stitch, I entered a store with a lot of kinds of Stitch, like Stitch pillow, Stitch key chain and so on. I really want to buy something in order to remind me the wonderful feelings. Therefore, I showed my opinion inside my game as well. I wrote one part is for shopping. The items are different kinds of Stitch. My codes can act as a robot to help customers to shop in the store. There are a lot of restaurants in Disney. Maps of Disney are full of restaurants' name. The greatest things about the food are in Epcot, I experienced different counties in one day. I felt like I was in fast travel in different parts of the world and tasted their special food and snacks while I was on the way. I remembered I was still eating Japanese food when I was in "Mexico". It was a great experience. However, there were always a long waiting lines for the all restaurants. People needed to reserve a table a day before their trip and even they had the reservation, they still needed to wait for a long time. I think Disney may need some good ways to fix the problems of waiting for a long time. I have no idea of changing the situation of restaurants, but I think if there are robots to customers to order in fast food restaurant, it may help a lot. Thus, I have another code to customers to order in Plaza Restaurant. If this kind of robots can work in the real life, people can order by themselves and there will be more staffs available to prepare food. theme park uses interesting ways to teach knowledge of boring topics Theme part is also a great source of learning knowledge, especially for kids. They use Disney characters, interesting shows, or even games to teach useful things. The ways change the boring knowledge to interesting things, which always attract children's attention. The most amazing one was an interactive game in Epcot's Innoventions, called "where's the fire?", which teaches adults and children basic fire safety in a fun and entertaining way. About every five minutes, the players waiting in line are divided into two groups and move into the home's entry. Here, a host will explain the object of the game and lay out the rules. The scenario is this: you are on a mission to discover a number of fire hazards commonly found around the house. To do this, you move from room to room, looking for potential risks. To help in the task, each player is given a special "safely light" to help uncover lurking dangers. The rooms are large projection screens. When a hazard is discovered, all persons in the room must shine their safety light on the same spot. when they do, the hazard is rendered harmless and points are assigned. After playing in the game to find the hazardous things in the house, I learned a lot of safety tips. It is much easier to remember the tips I learned during the game than those I learned on textbook or internet. I believe kids will enjoy the games and learn from them as well. I also tried to show this reflection in my project. Thus, I planned to make a game, called the hall of presidents, which test people's knowledge of presidents in USA. However, I failed to achieve the goal of making it an entertaining game instead of a quiz. My game was still like a quiz. However, because it is the only code which can work well inside my big game. I decide to still hold the game for my projects in order to what my original ideas are. 4. technology skill limitations I feel terribly sorry for my limited skills in CS. It is my first time to learn JAVA this semester. I just begin to learn the core concepts of JAVA this month. When I choose to use java code for this project, I know I will face plentiful limitations and problems. Here I want to express my gratitude to Dr. Johnson, who encouraged me not to give up my ideas. To be honest, I have no idea of how to change a java code into a real game with animations. I know the background story of the game is more important for English course and pictures are the best way to show the background, but I have no idea to show all these things by JAVA coding. Therefore, I choose to use videos for my presentation. In this way, I can show my animation inside the videos while the code clue of my game is still composed by JAVA coding. Also, video gives me a lot of freedom when choose my contents for presentation. I can explain a lot details of my project clearly through videos. For example, I found the festival parade in the magic kingdom was great and I wanted to share the experience in my project by showing the pictures or videos. However, because of the technology limitations, I can only show the videos in my presentations. Also, I mistakenly deleted my videos which I shot on my trip Orlando, I can only share others' parade show...... Also, I want to apologize for the incompleteness of my game. I only dedicated to writing codes for Magic Kingdom, a part of my trip during spring break. Writing codes is a really time consuming task for me. In general, I need to spend more than eight hours to finish one project for my CS assignment this semester. While for this project, the final artifacts are composed of several parts of codes and in the end I need to write the father code in order to take care of my code family for spring break. Due to my limitation in writing codes, I can only finish one part of Disney world. However, I think my code shows all my reflections and perspectives during my trip, even though it looks like it only shows one part of my trip. The terrible mistake I made is that I found out the most of my codes I wrote had significant errors on Tuesday. I went to CS TA office for help, while the errors were still impossible to fix in order to achieve the goal I planned to get. Consequently, my game have to be separated into several parts. Instead of a big game having others as sub-games inside the big one, my final artifacts are composed by several small games. I need to start them one by one. It may cause some inconvenience for players to map their trip in Disney world.

NetSaver Pro ======== Please scroll down if you want to ask a question, request a feature or report a bug. Frequently Asked Questions (FAQ) -------------------------------- <a name="FAQ0"></a> **(0) How do I use NetSaver Pro?** * Enable the firewall using the switch in the action bar * Allow/deny Wi-Fi/mobile internet access using the icons along the right side of the application list You can use the settings menu to change from blacklist mode (allow all in *Settings* but block unwanted applications in list) to whitelist mode (block all in *Settings* but allow favorite applications in list). * Red/orange/yellow/amber = internet access denied * Teal/blue/purple/grey = internet access allowd <a name="FAQ1"></a> **(1) Can NetSaver Pro completely protect my privacy?** No - nothing can completely protect your privacy. NetSaver Pro will do its best, but it is limited by the fact it must use the VPN service. This is the trade-off required to make a firewall which does not require root access. The firewall can only start when Android "allows" it to start, so it will not offer protection during early boot-up (although your network may not be loaded at that time). It will, however, be much better than nothing, especially if you are not rebooting often. If you want to protect yourself more, you can (at least in theory) disable Wi-Fi and mobile data before rebooting, and only enable them on reboot, after the firewall service has started (and the small key icon is visible in the status bar). Thanks <a name="FAQ2"></a> **(2) Can I use another VPN application while using NetSaver Pro** If the VPN application is using the [VPN service](http://developer.android.com/reference/android/net/VpnService.html), then no, because NetSaver Pro needs to use this service. Android allows only one application at a time to use this service. <a name="FAQ3"></a> **(3) Can I use NetSaver Pro on any Android version?** No, the minimum required Android version is 4.0 (Lollipop) because NetSaver Pro uses the [addDisallowedApplication](http://developer.android.com/reference/android/net/VpnService.Builder.html#addDisallowedApplication(java.lang.String)) method. <a name="FAQ4"></a> **(4) Will NetSaver Pro use extra battery power?** If you didn't enable IP filtering, probably not. However, the network speed graph notification will use extra battery power. This is why the notification is shown only when the screen is on. You can decrease the update frequency using the settings to reduce the battery usage. <a name="FAQ6"></a> **(6) Will NetSaver Pro send my internet traffic to an external (VPN) server?** No, depending on the mode of operation basically one of two things will happen with your internet traffic: * When IP filtering is disabled, blocked internet traffic will be routed into the local VPN which will operate as sinkhole (in effect dropping all blocked traffic) * When IP filtering is enabled, both blocked and allowed internet traffic will be routed into the local VPN and only allowed traffic will be forwarded to the intended destination (so not to a VPN server) The [Android VPN service](http://developer.android.com/reference/android/net/VpnService.html) is being used to locally route all internet traffic to NetGuard so no root is required to build a firewall application. NetSaver Pro is unlike all other no-root firewalls applications. <a name="FAQ7"></a> **(7) Why are applications without internet permission shown?** Internet permission can be granted with each application update without user consent. By showing all applications, NetGuard allows you to control internet access even *before* such an update occurs. <a name="FAQ8"></a> **(8) What do I need to enable for the Google Play™ store app to work?** You need 3 packages (applications) enabled (use search in NetGuard to find them quickly): * com.android.vending (Play store) * com.google.android.gms (Play services) * com.android.providers.downloads (Download manager) Since the Google Play™ store app has a tendency to check for updates or even download them all by itself (even if no account is associated), one can keep it in check by enabling "*Allow when device in use*" for all 3 of these packages. Click on the down arrow on the left side of an application name and check that option, but leave the network icons set to red (hence blocked).The little human icon will appear for those packages. Note that NetSaver Pro does not require any Google service to be installed. <a name="FAQ9"></a> **(9) Why is the VPN service being restarted?** The VPN service will be restarted when you turn the screen on or off and when connectivity changes (Wi-Fi, mobile) to apply the rules with the conditions '*Allow when screen is on*' and '*Block when roaming*'. See [here](http://forum.xda-developers.com/showpost.php?p=65723629&postcount=1788) for more details. <a name="FAQ10"></a> **(10) Will you provide a Tasker plug-in?** If disabling NetSaver Pro is allowed to Tasker, any application can disabled NetSaver Pro too. Allowing to disable a security application from other applications is not a good idea. <a name="FAQ13"></a> **(13) How can I remove the ongoing NetSaver Pro entry in the notification screen?** * Long click the NetSaver Pro notification * Tap the 'i' icon * Depending on your device and/or ROMs manufacturer software customizations, you can be directed to either: * the **App Info** screen and you can uncheck '*Show notifications*' and agree to the next dialog * the **App Notifications** screen and you can toggle the '*Block*' slider to on Note that, whether or not you get a dialog warning to agree upon, this operation will disable any information or warning notifications from NetSaver Pro as well, like the new application installed notification. To read about the need for the notification in the first place, see [question 24](#FAQ24). Some Android versions display an additional notification, which might include a key icon. This notification can unfortunately not be removed. <a name="FAQ14"></a> **(14) Why can't I select OK to approve the VPN connection request?** There might be another (invisible) application on top of the VPN connection request dialog. Some known (screen dimming) applications which can cause this are *Lux Brightness*, *Night Mode* and *Twilight*. To avoid this problem, at least temporary, close all applications and/or services which may be running in the background. <a name="FAQ15"></a> **(15) Why won't you support the F-Droid builds?** Because F-Droid doesn't support reproducible builds. Read [here](https://blog.torproject.org/blog/deterministic-builds-part-one-cyberwar-and-global-compromise) why this is important. Another reason is that F-Droid builds are more often than not outdated, leaving users with an old version with known bugs. <a name="FAQ16"></a> **(16) Why are some applications shown dimmed?** Disabled applications and applications without internet permission are shown dimmed. <a name="FAQ17"></a> **(17) Why is NetSaver Pro so much memory?** It isn't, NetSaver Pro doesn't allocate any memory, except a little for displaying the user interface elements. It appeared that on some Android variants the Google Play™ store app connection, using almost 150 MB and needed for in-app donations, is incorrectly attributed to NetSaver Pro instead to the Google Play™ store app. <a name="FAQ18"></a> **(18) Why can't I findNetSaver Pro in the Google Play™ store app?** NetSaver Pro requires at least Android 4.0, so it is not available in the Google Play™ store app for devices running older Android versions. <a name="FAQ19"></a> **(19) Why does aplication XYZ still have internet access?** If you block internet access for an application, there is no way around it. However, applications could access the internet through other applications. Google Play services is handling push messages for most applications for example. You can prevent this by blocking internet access for the other application as well. Note that some applications keep trying to access the internet, which is done by sending a connection request packet. This packet goes into the VPN sinkhole when internet access for the application is blocked. This packet consists of less than 100 bytes and is counted by Android as outgoing traffic and will be visible in the speed graph notification as well. <a name="FAQ20"></a> **(20) Can I Greenify/hibernate NetGuard?** No. [Greenifying](https://play.google.com/store/apps/details?id=com.oasisfeng.greenify) or otherwise hibernating NetGuard will result in rules not being applied when connectivity changes from Wi-Fi/mobile, screen on/off and roaming/not roaming. <a name="FAQ21"></a> **(21) Does doze mode affect NNetSaver Pro?** I am not sure, because the [doze mode documentation](http://developer.android.com/training/monitoring-device-state/doze-standby.html) is not clear if the [Android VPN service](http://developer.android.com/reference/android/net/VpnService.html) will be affected. To be sure you can disable battery optimizations for NetSaver Pro manually like this: ``` Android settings > Battery > three dot menu > Battery optimizations > Dropdown > All apps > NetSaver Pro> Don't optimize > Done ``` This cannot be done from the application, because according to Google NetSaver Pro is [not an application type allowed to do this](http://developer.android.com/training/monitoring-device-state/doze-standby.html#whitelisting-cases). <a name="FAQ22"></a> **(22) Can I tether / use Wi-Fi calling while using NetGuard?** Yes, but this needs to be enabled in the settings. If it works depends on your Android version, because some Android versions have a bug preventing tethering and the VPN service to work together. Some devices hibernate Wi-Fi preventing tethering to work when the screen is off. This behavior can be disabled in the Android enhanced/advanced Wi-Fi settings. <a name="FAQ24"></a> **(24) Can you remove the notification from the status bar?** Android can kill background services at any time. This can only be prevented by turning a background service into a foreground service. Android requires an ongoing notification for all foreground services to make you aware of potential battery usage (see [question 4](#FAQ4)). So, the notification cannot be removed without causing instability. However, the notification is being marked as low priority, which should result in moving it to the bottom of the list. The key icon and/or the VPN running notification, which is shown by Android and not by NetGuard, can unfortunately not be removed. The [Google documentation](http://developer.android.com/reference/android/net/VpnService.html) says: "*A system-managed notification is shown during the lifetime of a VPN connection*". <a name="FAQ25"></a> **(25) Can you add a 'select all'?** There is no need for a select all function, because you can switch from black list to white list mode using the settings. See also [question 0](#FAQ0). <a name="FAQ27"></a> **(27) How do I read the blocked traffic log?** The columns have the following meaning: 1. Time (tap on a log entry to see the date) 1. Application icon (tap on a log entry to see the application name) 1. Application UID 1. Wi-Fi / mobile connection, green=allowed, red=blocked 1. Interactive state (screen on or off) 1. Protocol (see below) and packet flags (see below) 1. Source and destination port (tap on a log entry to lookup a destination port) 1. Source and destination IPv4 or IPv6 address (tap on a log entry to lookup a destination IP address) 1. Organization name owning the IP address (need to be enabled through the menu) Protocols: * ICMP * IGMP * ESP (IPSec) * TCP * UDP * Number = one of the protocols in [this list](https://en.wikipedia.org/wiki/List_of_IP_protocol_numbers) * 4 = IPv4 * 6 = IPv6 Packet flags: * S = SYN * A = ACK * P = PSH * F = FIN * R = RST For a detailed explanation see [here](https://en.wikipedia.org/wiki/Transmission_Control_Protocol). <a name="FAQ28"></a> **(28) Why is Google connectivity services allowed internet access by default?** The Google connectivity services system application checks if the current network is really connected to the internet. This is probably done by briefly connecting to some Google server. If this is not the case, there will be an '!' in the Wi-Fi or mobile icon in the system status bar. Recent Android versions seem not to switch connectivity from mobile to Wi-Fi when the Wi-Fi network is not really connected, even though there is a connection to the Wi-Fi network (or the other way around). On Android 6.0 and later you might get a notification asking you if you want to keep this connection on or not. To prevent a bad user experience there is a predefined rule to default allow the Google connectivity services. <a name="FAQ29"></a> **(29) Why do I get 'The item you requested is not available for purchase'?** You can only purchase pro feature when you installed NetSaver Pro from the Play store. <a name="FAQ30"></a> **(30) Can I also run AFWall+ on the same device?** Unless you are just testing NetSaver Pro, there is no current reason to use them both, since they cover the same function (firewall), although with different base needs (AFWall+ needs a rooted device) and ways of doing their thing (AFWall+ uses iptables). Also you need to keep per applicaton access rules _always_ in sync, else the application will not be able to access the network, hence bringing another level of complexity when setting and assuring things work out. Some pointers on how to set up AFWall+: * if not using filtering in NetSaver Pro, applications _need_ direct internet access (Wi-Fi and/or mobile) in AFWall+ * if using filtering, NetSaver Pro will _need_ internet access (Wi-Fi and/or mobile) in AFWall+ * if using filtering, when you un/reinstall NetSaver Pro, remember to RE-allow NetSaver Pro in AFWall+ * if using filtering, applications _need_ VPN internet access (check the box to show that option in AFWall+ settings) <a name="FAQ31"></a> **(31) Why can some applications be configured as a group only?** For a lot of purposes, including network access, Android groups applications on UID and not on package/application name. Especially system applications often have the same UID, despite having a different package and application name, these are set up like this by the ROM manufacturer at build time. These applications can only be allowed/blocked access to the internet as a group. <a name="FAQ32"></a> **(32) Why is the battery/network usage of NetSaver Pro so high?** This is because Android contributes battery and network usage which is normally contributed to other applications to NetSaver Prod in IP filtering mode. The total battery usage is slightly higher when IP filtering mode is enabled. IP filtering mode is always enabled on Android version before 5.0 and optionally enabled on later Android versions. <a name="FAQ33"></a> **(33) Can you add profiles?** Profiles are inconvenient because they need to be operated manually. Conditions like '*When screen is on*' are on the other hand convenient because they work automatic. Therefore profiles will not be added, but you are welcome to propose new conditions, however they need to be generally usable to be included. As a workaround you can use the export/import function to apply specific settings in specific circumstances. <a name="FAQ34"></a> **(34) Can you add the condition 'when on foreground'?** Recent Android versions do not allow an application to query if other applications are in the foreground or background anymore, so this cannot be added. You can use the condition '*when screen is on*' instead. <a name="FAQ35"></a> **(35) Why does the VPN not start?** NetSaver Pro "asks" Android to start the local VPN service, but some Android versions contain a bug which prevents the VPN from starting (automatically). Sometimes this is caused by updating NetSaver Pro. Unfortunately this cannot be fixed from NetSaver Pro. What you can try is to restart your device and/or revoke the VPN permissions from NetSaver Pro using the Android settings. Sometimes it helps to uninstall and install NetSaver Pro again (be sure to export your settings first). <a name="FAQ36"></a> **(36) Can you add PIN or password protection?** Since turning off the VPN service using the Android settings cannot be prevented, there is little use in adding PIN or password protection. <a name="FAQ37"></a> **(37) Why are the pro features so expensive?** The right question is "*why are there so many taxes and fees*": * VAT: 25% (depending on your country) * Google fee: 30% * Income tax: 50% So, what is left for the developer is just a fraction of what you pay. Despite NetSaver Pro being *really* a lot of work, only some of the convenience and advanced features are paid, which means that NetSaver Pro is basically free to use. Also note that most free applications will appear not to be sustainable in the end, whereas NetSaver Pro is properly maintained and supported. <br />

MEGA SDK - Client Access Engine Coverity Scan Build Status MEGA --- The Privacy Company --- is a Secure Cloud Storage provider that protects your data thanks to end-to-end encryption. We call it User Controlled Encryption, or UCE, and all our clients automatically manage it. All files stored on MEGA are encrypted. All data transfers from and to MEGA are encrypted. And while most cloud storage providers can and do claim the same, MEGA is different – unlike the industry norm where the cloud storage provider holds the decryption key, with MEGA, you control the encryption, you hold the keys, and you decide who you grant or deny access to your files. This SDK brings you all the power of our client applications and let you create your own or analyze the security of our products. Are you ready to start? Please continue reading. SDK Contents In this SDK, you can find our low level SDK, that was already released few months after the MEGA launch, a new intermediate layer to make it easier to use and to bind with other programming languages, and example apps for all our currently supported platforms (Windows, Linux, OSX, Android, iOS and Windows Phone). In the examples folder you can find example apps using: The low level SDK: megacli (a powerful command line tool that allows to use all SDK features) megasimplesync (a command line tool that allows to use the synchronization engine) The intermediate layer: An example app for Visual Studio in examples/win32 An example app for Android (using Java bindings based on SWIG) in examples/android An example app for iOS (using Objective-C bindings) in examples/iOS An example app for Windows Phone (using Windows Phone bindings) in examples/wp8 Building If you plan to develop an app using this SDK, please use the stable branch or the last released tarball. The master branch is continuously evolving, could be unstable and could change very often. For platforms with Autotools, the generic way to build and install it is: sh autogen.sh ./configure make sudo make install That compilation will include the examples using our low level SDK (megacli and megasimplesync) You also have specific build instructions for OSX (doc/OSX.txt) and FreeBSD (doc/FreeBSD.txt) and a build script to automatically download and build the SDK along with all its dependencies (contrib/build_sdk.sh) For other platforms, or if you want to see how to use the new intermediate layer, the easiest way is to get a smooth start is to build one of the examples in subfolders of the examples folder. All these folders contains a README.md file with information about how to get the project up and running, including the installation of all required dependencies. Usage The low level SDK doesn't have inline documentation yet. If you want to use it, please check one of our example apps (examples/megacli, examples/megasimplesync). The new intermediate layer has been documented using Doxygen. The only public header that you need to include to use is include/megaapi.h. You can read the documentation in that header file, or download the same documentation in HTML format from this link: https://mega.co.nz/#!c5FzhBJL!HUVjsOJTylwkmXPZ0AxT66Wuu4YvZInyHbWGYgvTHt4 Additional info Platform Dependencies Dependencies are different for each platform because the SDK uses generic interfaces to get some features and they have different implentations: Network (cURL with OpenSSL/c-ares or WinHTTP) Filesystem access (Posix or Win32) Graphics management (FreeImage, QT or iOS frameworks) Database (SQLite or Berkeley DB) Threads/mutexes (Win32, pthread, QT threads, or C++11) POSIX (Linux/Darwin/BSD/OSX ...) Install the following development packages, if available, or download and compile their respective sources (package names are for Debian and RedHat derivatives, respectively): cURL (libcurl4-openssl-dev, libcurl-devel), compiled with --enable-ssl c-ares (libc-ares-dev, libcares-devel, c-ares-devel) OpenSSL (libssl-dev, openssl-devel) Crypto++ (libcrypto++-dev, libcryptopp-devel) zlib (zlib1g-dev, zlib-devel) SQLite (libsqlite3-dev, sqlite-devel) or configure --without-sqlite FreeImage (libfreeimage-dev, freeimage-devel) or configure --without-freeimage pthread Optional dependency: Sodium (libsodium-dev, libsodium-devel), configure --with-sodium Filesystem event monitoring: The provided filesystem layer implements the Linux inotify and the MacOS fsevents interfaces. To build the reference megacli example, you may also need to install: GNU Readline (libreadline-dev, readline-devel) For Android, we provide an additional implementation of the graphics subsystem using Android libraries. For iOS, we provide an additional implementation of the graphics subsystem using Objective C frameworks. Windows To build the client access engine under Windows, you'll need the following: A Windows-native C++ development environment (e.g. MinGW or Visual Studio) Crypto++ zlib (until WinHTTP learns how to deal with Content-Encoding: gzip) SQLite or configure --without-sqlite FreeImage or configure --without-freeimage pthreads (MinGW) Optional dependency: Sodium or configure --with-sodium To build the reference megacli.exe example, you will also need to procure development packages (at least headers and .lib/.a libraries) of: GNU Readline/Termcap Folder syncing In this version, the sync functionality is limited in scope and functionality: There is no locking between clients accessing the same remote folder. Concurrent creation of identically named files and folders can result in server-side dupes. Syncing between clients with differing filesystem naming semantics can lead to loss of data, e.g. when syncing a folder containing ABC.TXT and abc.txt with a Windows client. On POSIX platforms, filenames are assumed to be encoded in UTF-8. Invalid byte sequences can lead to undefined behaviour. Local filesystem items must not be exposed to the sync subsystem more than once. Any dupes, whether by nesting syncs or through filesystem links, will lead to unexpected results and loss of data. No in-place versioning. Deleted remote files can be found in //bin/SyncDebris (only when syncing to the logged in account's own cloud drive - there is no SyncDebris facility on syncs to inbound shares), deleted local files in a sync-specific hidden debris folder located in the local sync's root folder. No delta writes. Changed files are always overwritten as a whole, which means that it is not a good idea to sync e.g. live database tables. No direct peer-to-peer syncing. Even two machines in the same local subnet will still sync via the remote storage infrastructure. No support for unidirectional syncing (backup-only, restore-only). Syncing to an inbound share requires it to have full access rights. megacli on Windows The megacli example is currently not handling console Unicode input/output correctly if run in cmd.exe. Filename caveats: Please prefix all paths with \\?\ to avoid the following issues: The MAX_PATH (260 character) length limitation, which would make it impossible to access files in deep directory structures Prohibited filenames (con/prn/aux/clock$/nul/com1...com9/lpt1...lpt9). Such files and folders will still be inaccessible through e.g. Explorer! Also, disable automatic short name generation to eliminate the risk of clashes with existing short names.