2. Add the property name with the value John.

3. Add the property surname with the value Smith.

4. Change the value of name to Pete.

5. Delete the property name from the object.

Determine if an object is empty

Create a function isEmpty(obj) that returns true if the object has no properties and false if there is at least one property.

It should work like this:

  function isEmpty(obj) {
    /* your code */
  }

  var schedule = {};

  alert( isEmpty(schedule) ); // true

  schedule["8:30"] = "wake up";

  alert( isEmpty(schedule) ); // false

Result: isEmpty

Sum of properties

There is a salaries object with salaries. Write code that outputs the sum of all salaries.

If the object is empty, the result should be 0.

For example:

 "use strict";

 var salaries = {
   "John": 100,
   "Pete": 300,
   "Mary": 250
 };

 //... your code should output 650

Result: sumObj

Property with the largest value

There is a salaries object with salaries. Write code that outputs the name of the employee with the highest salary.

If the object is empty, it should output "no employees".

For example:

   "use strict";

   var salaries = {
     "John": 100,
     "Pete": 300,
     "Mary": 250
    };

   // ... your code should output "Pete"

Result: maxValue

Multiply numeric properties by 2

Create a function multiplyNumeric that takes an object and multiplies all numeric properties by 2.

For example:

     // before the call
     var menu = {
       width: 200,
       height: 300,
       title: "My menu"
     };

     multiplyNumeric(menu);

     // after the call
     menu = {
       width: 400,
       height: 600,
       title: "My menu"
     };

Result: multiplyNumeric

Get the last element of an array

How do you get the last element from an arbitrary array?

We have an array goods. We don't know how many elements it has, but we can read it from goods.length.

Write code to get the last element of goods.

Result: operationArray

Add a new element to an array

How do you add an element to the end of an arbitrary array?

We have an array goods. Write code to add the value "Computer" to its end.

Result: operationArray

Creating an array

A task with 5 step-lines:

Create an array styles with elements "Jazz", "Blues".

Add the value "Rock-n-Roll" to the end.

Replace the second-to-last value with "Classical". The code for replacing the second-to-last value should work for arrays of any length.

Remove the first value of the array and display it with alert.

Add the values "Rap" and "Reggae" to the beginning.

The array at each step:

   Jazz, Blues
   Jazz, Blues, Rock-n-Roll
   Jazz, Classical, Rock-n-Roll
   Classical, Rock-n-Roll
   Rap, Reggae, Classical, Rock-n-Roll

Result: operationArray

Get a random value from an array

Write code to alert a random value from the array:

  var arr = ["Apple", "Orange", "Pear", "Lemon"];

P.S. Code to generate a random integer from min to max inclusive:

  var rand = min + Math.floor(Math.random() * (max + 1 - min));

Result: randElemArray

Create a calculator for entered values

Write code that:

• 1. Asks for values one by one using prompt and stores them in an array.
• 2. Stops input when the user enters an empty string, a non-number, or presses "Cancel".
• 3. Zero (0) should not stop the input, it is an allowed number.
• 4. Outputs the sum of all array values.

Result: calcArray

Search in an array

Create a function find(arr, value) that searches for value in array arr and returns its index if found, or -1 if not found.

For example:

  arr = ["test", 2, 1.5, false];

  find(arr, "test"); // 0
  find(arr, 2); // 1
  find(arr, 1.5); // 2

  find(arr, 0); // -1

Result: find(arr, value)

Range filter

Create a function filterRange(arr, a, b) that takes an array of numbers arr and returns a new array containing only numbers from arr in the range from a to b. That is, the check is a ≤ arr[i] ≤ b. The function should not modify arr.

Example usage:

   var arr = [5, 4, 3, 8, 0];

   var filtered = filterRange(arr, 3, 5);
   // now filtered = [5, 4, 3]
   // arr is not modified

Result: filterRange(arr, a, b)

Add a class to a string

An object has a className property that contains a list of "classes" – words separated by spaces:

 var obj = {
   className: 'open menu'
 }

Create a function addClass(obj, cls) that adds the class cls to the list, but only if it's not already there:

 addClass(obj, 'new'); // obj.className='open menu new'
 addClass(obj, 'open'); // no changes (class already exists)
 addClass(obj, 'me'); // obj.className='open menu new me'

 alert( obj.className ); // "open menu new me"

P.S. Your function should not add extra spaces.

Result: addNewClass

Convert text like border-left-width to borderLeftWidth

Write a function camelize(str) that converts strings like "my-short-string" to "myShortString".

That is, hyphens are removed and all words after them get an uppercase first letter.

For example:

   camelize("background-color") == 'backgroundColor';
   camelize("list-style-image") == 'listStyleImage';
   camelize("-webkit-transition") == 'WebkitTransition';

Such a function is useful when working with CSS.

Result: camelize(str)

Function removeClass

An object has a className property that stores a list of "classes" – words separated by spaces:

    var obj = {
      className: 'open menu'
    };

Write a function removeClass(obj, cls) that removes the class cls if it exists:

   removeClass(obj, 'open'); // obj.className='menu'
   removeClass(obj, 'blabla'); // no changes