sql-highlight

A simple and lightweight library for highlighting SQL queries written in pure JavaScript

What's it all about?

sql-highlight is a small package that highlights SQL queries. It can output to both the terminal with Unicode escape sequences, as well as to normal HTML. Oh, and there are no external dependencies 😉

Installation

sql-highlight is tested to work with Node.js 16, 18, 20, 22 and 24.

Install with Yarn:

yarn add sql-highlight

Install with NPM:

npm install sql-highlight

Usage

In its most basic form

const { highlight } = require('sql-highlight')

const sqlString = "SELECT `id`, `username` FROM `users` WHERE `email` = 'test@example.com'"

const highlighted = highlight(sqlString)

console.log(highlighted)

Output:

HTML mode

const { highlight } = require('sql-highlight')

const sqlString = "SELECT `id`, `username` FROM `users` WHERE `email` = 'test@example.com'"

const highlighted = highlight(sqlString, {
  html: true
})

document.body.innerHTML += highlighted

Output:

<span class="sql-hl-keyword">SELECT</span>
<span class="sql-hl-identifier">`id`</span>
<span class="sql-hl-special">,</span>
<span class="sql-hl-identifier">`username`</span>
<span class="sql-hl-keyword">FROM</span>
<span class="sql-hl-identifier">`users`</span>
<span class="sql-hl-keyword">WHERE</span>
<span class="sql-hl-identifier">`email`</span>
<span class="sql-hl-special">=</span>
<span class="sql-hl-string">'test@example.com'</span>

Sample styles to get you going can be found in sample-style.css. To use them, append the output to a code tag with the class name sql, like this:

<code class="sql">
  <span class="sql-hl-keyword">SELECT</span>
  <span class="sql-hl-identifier">`id`</span>
  <!-- etc... -->
</code>

Options

The following options may be passed to the highlight function.

Option	Value	Default	Description
html	boolean	false	Set to true to render HTML instead of Unicode.
htmlEscaper	(str: string) => string	Basic escaper	Function to escape HTML entities. Uses a basic escaper by default. If HTML mode is used in a browser environment this could be useful to escape strings using the DOM.
classPrefix	string	'sql-hl-'	Prefix to prepend to classes for HTML span-tags. Is appended with entity name.
colors	Object	See below*	What color codes to use for Unicode rendering. A list of basic color codes can be found here.

* colors option default value

{
  keyword: '\x1b[35m',  // SQL reserved keywords
  function: '\x1b[31m', // Functions
  number: '\x1b[32m',   // Numbers
  string: '\x1b[32m',   // Strings
  special: '\x1b[33m',  // Special characters
  bracket: '\x1b[33m',  // Brackets (parentheses)
  comment: '\x1b[2m\x1b[90m', // Comments
  clear: '\x1b[0m'      // Clear (inserted after each match)
}

Custom highlighting

In case you want to do the highlighting yourself you can use getSegments to only let sql-highlight parse the SQL string for you. You can then use the segments to highlight it yourself.

const { getSegments } = require('sql-highlight')

const sqlString = "SELECT `id`, `username` FROM `users` WHERE `email` = 'test@example.com'"

const segments = getSegments(sqlString)

console.log(segments)

Output:

[
    { name: 'keyword', content: 'SELECT' },
    { name: 'whitespace', content: ' ' },
    { name: 'identifier', content: '`id`' },
    { name: 'special', content: ',' },
    { name: 'whitespace', content: ' ' },
    { name: 'identifier', content: '`username`' },
    { name: 'whitespace', content: ' ' },
    { name: 'keyword', content: 'FROM' },
    { name: 'whitespace', content: ' ' },
    { name: 'identifier', content: '`users`' },
    { name: 'whitespace', content: ' ' },
    { name: 'keyword', content: 'WHERE' },
    { name: 'whitespace', content: ' ' },
    { name: 'identifier', content: '`email`' },
    { name: 'whitespace', content: ' ' },
    { name: 'special', content: '=' },
    { name: 'whitespace', content: ' ' },
    { name: 'string', content: "'test@example.com'" }
]

Contributing

See the contribution guidelines.

Tests

We use Jest for running our tests. The test suite can be run by running npm run test. This will run both Jest and Biome.

Code style

We use Biome for making sure that our code remains pretty and consistent throughout the project. If your editor doesn't automatically pick up our config you can lint the code using npm run lint.

A note on Dependabot

Dependabot Auto Merge is installed in this repository to automatically merge dependabot PRs for minor version updates. Only PRs that pass the tests get merged. No new releases will be created for dependency updates as there are no production dependencies and a release would therefore be completely unnecessary.

Additional information

Malcolm Nihlén - malcolm.nihlen@gmail.com

Distributed under the MIT licence. See LICENCE for more information.

https://github.com/scriptcoded

Disclaimer

This was initially a fork from https://github.com/pomahtuk/sequilize-highlight. The repo wasn't being updated, NPM wasn't serving the latest version and there was a severe memory leak. Though the latest version now exists on NPM, issues still persist. This repo serves to address those problems, as well as providing a cleaner interface that's not bound to Sequelize.

With version 3.0.0 the library was almost completely rewritten, which leaves very little similarity with the original repo.