js-beautify

Beautifier for javascript

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Quick Overview

js-beautify is a JavaScript beautifier, formatter, and pretty-printer. It takes JavaScript code as input and outputs a formatted version with consistent indentation, spacing, and line breaks. The project aims to improve code readability and maintainability.

Pros

Supports multiple languages: JavaScript, JSON, CSS, HTML, and XML
Configurable formatting options to match different coding styles
Available as a command-line tool, Node.js library, and browser-based tool
Actively maintained with regular updates and bug fixes

Cons

May not handle all edge cases or complex code structures perfectly
Some users report inconsistencies in formatting results across different versions
Limited support for newer JavaScript features and syntax
Can be slow when processing large files or projects

Code Examples

Beautifying JavaScript code:

const beautify = require('js-beautify').js;

const uglyCode = 'function foo(){return{bar:function(){},baz:function(){}}}';
const beautifiedCode = beautify(uglyCode, { indent_size: 2, space_in_empty_paren: true });

console.log(beautifiedCode);

Beautifying HTML code:

const beautify = require('js-beautify').html;

const uglyHtml = '<div><p>Hello,<span>World!</span></p></div>';
const beautifiedHtml = beautify(uglyHtml, { indent_size: 2, wrap_line_length: 80 });

console.log(beautifiedHtml);

Beautifying CSS code:

const beautify = require('js-beautify').css;

const uglyCss = '.class1{color:red;}.class2{background-color:blue;}';
const beautifiedCss = beautify(uglyCss, { indent_size: 2, newline_between_rules: true });

console.log(beautifiedCss);

Getting Started

To use js-beautify in your Node.js project:

Install the package:
```
npm install js-beautify
```

Import and use the library:

const beautify = require('js-beautify').js;
const uglyCode = 'function foo() { return "bar"; }';
const beautifiedCode = beautify(uglyCode, { indent_size: 2 });
console.log(beautifiedCode);

For command-line usage, install globally:

npm install -g js-beautify

Then use it in the terminal:

js-beautify input.js > output.js

Competitor Comparisons

prettier

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Prettier is an opinionated code formatter.

Pros of Prettier

Opinionated formatting with minimal configuration options, leading to consistent code style across projects
Supports a wider range of languages and file types, including JSX, TypeScript, CSS, and more
Actively maintained with frequent updates and improvements

Cons of Prettier

Less flexibility in customizing formatting rules compared to js-beautify
May require more setup and integration with build tools for optimal use

Code Comparison

js-beautify:

function example(foo,bar,baz){
    if(foo){
        return bar;
    }else{
        return baz;
    }
}

Prettier:

function example(foo, bar, baz) {
  if (foo) {
    return bar;
  } else {
    return baz;
  }
}

Key Differences

Prettier enforces a more opinionated style with consistent spacing and line breaks
js-beautify offers more granular control over formatting rules
Prettier supports modern JavaScript features and frameworks out of the box
js-beautify focuses primarily on JavaScript and HTML formatting

Use Cases

Choose Prettier for projects prioritizing consistent style across teams
Opt for js-beautify when more fine-grained control over formatting is required

terser

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🗜 JavaScript parser, mangler and compressor toolkit for ES6+

Pros of Terser

Minifies and compresses JavaScript code, resulting in smaller file sizes
Offers advanced optimization techniques like dead code elimination and scope hoisting
Actively maintained with frequent updates and improvements

Cons of Terser

Primarily focused on minification rather than beautification
May produce less readable code due to its optimization techniques
Steeper learning curve for configuring advanced options

Code Comparison

js-beautify:

function example(x) {
    if (x > 0) {
        return x * 2;
    } else {
        return x / 2;
    }
}

Terser (minified output):

function example(x){return x>0?2*x:x/2}

Key Differences

js-beautify focuses on improving code readability and formatting
Terser aims to reduce code size and optimize performance
js-beautify is better suited for development environments
Terser is more appropriate for production builds and deployment

Use Cases

Use js-beautify when working on source code or debugging
Use Terser when preparing code for production or reducing file sizes

Community and Ecosystem

Both projects have active communities and are widely used
js-beautify has integrations with various text editors and IDEs
Terser is commonly used in build tools and bundlers like webpack

UglifyJS

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JavaScript parser / mangler / compressor / beautifier toolkit

Pros of UglifyJS

Minifies and compresses JavaScript code, reducing file size
Performs advanced optimizations like dead code elimination and variable renaming
Supports source maps for easier debugging of minified code

Cons of UglifyJS

Primarily focused on minification, not code beautification
May alter code structure and variable names, making it less readable
Can potentially break code if not used carefully, especially with certain JavaScript features

Code comparison

js-beautify:

function example(x) {
    if (x > 0) {
        return x * 2;
    } else {
        return x - 1;
    }
}

UglifyJS (minified output):

function example(x){return x>0?2*x:x-1}

Key differences

js-beautify focuses on improving code readability and formatting
UglifyJS aims to reduce code size and optimize performance
js-beautify preserves variable names and code structure
UglifyJS can significantly alter code structure for optimization

Both tools serve different purposes in the JavaScript development workflow. js-beautify is ideal for improving code readability and maintaining consistent style, while UglifyJS is essential for preparing code for production by minimizing file size and enhancing performance.

standard

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🌟 JavaScript Style Guide, with linter & automatic code fixer

Pros of Standard

Enforces a consistent, opinionated style out of the box
Includes linting rules for catching potential errors and bad practices
Integrates well with many editors and build tools

Cons of Standard

Less flexible for customization of formatting rules
May conflict with existing project styles or preferences
Stricter rules can be challenging for beginners or teams transitioning

Code Comparison

Standard:

function example (arg1, arg2) {
  if (arg1 && arg2) {
    return true
  }
  return false
}

js-beautify:

function example(arg1, arg2) {
    if (arg1 && arg2) {
        return true;
    }
    return false;
}

Key Differences

Standard omits semicolons and uses single quotes by default
js-beautify focuses on formatting without enforcing specific coding styles
Standard includes linting rules, while js-beautify is primarily for code formatting
js-beautify offers more customization options for formatting preferences
Standard aims to reduce decision-making about style, while js-beautify allows more flexibility

Both tools serve different purposes: Standard is a linter and style enforcer, while js-beautify is a code formatter. The choice between them depends on project requirements, team preferences, and the desired level of style enforcement.

eslint

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Find and fix problems in your JavaScript code.

Pros of ESLint

More comprehensive: ESLint offers both code formatting and linting capabilities, detecting potential errors and enforcing coding standards
Highly configurable: Provides extensive customization options for rules and plugins
Active development: Regularly updated with new features and improvements

Cons of ESLint

Steeper learning curve: Requires more initial setup and configuration
Potentially slower: Can be slower than js-beautify for large codebases due to its more extensive analysis

Code Comparison

js-beautify:

function example(a,b){
return a+b;}

ESLint (with auto-fix):

function example(a, b) {
  return a + b;
}

Key Differences

js-beautify focuses solely on code formatting, while ESLint combines formatting and linting
ESLint offers more granular control over coding style and best practices
js-beautify is simpler to set up and use for basic formatting needs
ESLint provides a more comprehensive toolset for maintaining code quality

Use Cases

js-beautify: Quick and simple code formatting tasks
ESLint: Comprehensive code quality management in larger projects or teams

Both tools have their merits, and the choice depends on project requirements, team preferences, and the desired level of code quality enforcement.

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README

JS Beautifier

This little beautifier will reformat and re-indent bookmarklets, ugly JavaScript, unpack scripts packed by Dean Edwardâs popular packer, as well as partly deobfuscate scripts processed by the npm package javascript-obfuscator.

Open beautifier.io to try it out. Options are available via the UI.

Contributors Needed

I'm putting this front and center above because existing owners have very limited time to work on this project currently. This is a popular project and widely used but it desperately needs contributors who have time to commit to fixing both customer facing bugs and underlying problems with the internal design and implementation.

If you are interested, please take a look at the CONTRIBUTING.md then fix an issue marked with the "Good first issue" label and submit a PR. Repeat as often as possible. Thanks!

Installation

You can install the beautifier for Node.js or Python.

Node.js JavaScript

You may install the NPM package js-beautify. When installed globally, it provides an executable js-beautify script. As with the Python script, the beautified result is sent to stdout unless otherwise configured.

$ npm -g install js-beautify
$ js-beautify foo.js

You can also use js-beautify as a node library (install locally, the npm default):

$ npm install js-beautify

Node.js JavaScript (vNext)

The above install the latest stable release. To install beta or RC versions:

$ npm install js-beautify@next

Web Library

The beautifier can be added on your page as web library.

JS Beautifier is hosted on two CDN services: cdnjs and rawgit.

To pull the latest version from one of these services include one set of the script tags below in your document:

<script src="https://cdnjs.cloudflare.com/ajax/libs/js-beautify/1.15.1/beautify.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/js-beautify/1.15.1/beautify-css.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/js-beautify/1.15.1/beautify-html.js"></script>

<script src="https://cdnjs.cloudflare.com/ajax/libs/js-beautify/1.15.1/beautify.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/js-beautify/1.15.1/beautify-css.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/js-beautify/1.15.1/beautify-html.min.js"></script>

Example usage of a JS tag in html:

<!DOCTYPE html>
<html lang="en">
  <body>

. . .

    <script src="https://cdnjs.cloudflare.com/ajax/libs/js-beautify/1.15.1/beautify.min.js"></script>
    <script src="script.js"></script>
  </body>
</html>

Older versions are available by changing the version number.

Disclaimer: These are free services, so there are no uptime or support guarantees.

Python

To install the Python version of the beautifier:

$ pip install jsbeautifier

Unlike the JavaScript version, the Python version can only reformat JavaScript. It does not work against HTML or CSS files, but you can install css-beautify for CSS:

$ pip install cssbeautifier

Usage

You can beautify JavaScript using JS Beautifier in your web browser, or on the command-line using Node.js or Python.

Web Browser

Open beautifier.io. Options are available via the UI.

Web Library

After you embed the <script> tags in your html file, they expose three functions: js_beautify, css_beautify, and html_beautify

Example usage of beautifying a json string:

const options = { indent_size: 2, space_in_empty_paren: true }

const dataObj = {completed: false,id: 1,title: "delectus aut autem",userId: 1,}

const dataJson = JSON.stringify(dataObj)

js_beautify(dataJson, options)

/* OUTPUT
{
  "completed": false,
  "id": 1,
  "title": "delectus aut autem",
  "userId": 1,
}
*/

Node.js JavaScript

When installed globally, the beautifier provides an executable js-beautify script. The beautified result is sent to stdout unless otherwise configured.

$ js-beautify foo.js

To use js-beautify as a node library (after install locally), import and call the appropriate beautifier method for JavaScript (JS), CSS, or HTML. All three method signatures are beautify(code, options). code is the string of code to be beautified. options is an object with the settings you would like used to beautify the code.

The configuration option names are the same as the CLI names but with underscores instead of dashes. For example, --indent-size 2 --space-in-empty-paren would be { indent_size: 2, space_in_empty_paren: true }.

var beautify = require('js-beautify/js').js,
    fs = require('fs');

fs.readFile('foo.js', 'utf8', function (err, data) {
    if (err) {
        throw err;
    }
    console.log(beautify(data, { indent_size: 2, space_in_empty_paren: true }));
});

If you are using ESM Imports, you can import js-beautify like this:

// 'beautify' can be any name here.
import beautify from 'js-beautify';

beautify.js(data, options);
beautify.html(data, options);
beautify.css(data, options);

Python

After installing, to beautify using Python:

$ js-beautify file.js

Beautified output goes to stdout by default.

To use jsbeautifier as a library is simple:

import jsbeautifier
res = jsbeautifier.beautify('your JavaScript string')
res = jsbeautifier.beautify_file('some_file.js')

...or, to specify some options:

opts = jsbeautifier.default_options()
opts.indent_size = 2
opts.space_in_empty_paren = True
res = jsbeautifier.beautify('some JavaScript', opts)

The configuration option names are the same as the CLI names but with underscores instead of dashes. The example above would be set on the command-line as --indent-size 2 --space-in-empty-paren.

Options

These are the command-line flags for both Python and JS scripts:

CLI Options:
  -f, --file       Input file(s) (Pass '-' for stdin)
  -r, --replace    Write output in-place, replacing input
  -o, --outfile    Write output to file (default stdout)
  --config         Path to config file
  --type           [js|css|html] ["js"] Select beautifier type (NOTE: Does *not* filter files, only defines which beautifier type to run)
  -q, --quiet      Suppress logging to stdout
  -h, --help       Show this help
  -v, --version    Show the version

Beautifier Options:
  -s, --indent-size                 Indentation size [4]
  -c, --indent-char                 Indentation character [" "]
  -t, --indent-with-tabs            Indent with tabs, overrides -s and -c
  -e, --eol                         Character(s) to use as line terminators.
                                    [first newline in file, otherwise "\n]
  -n, --end-with-newline            End output with newline
  --editorconfig                    Use EditorConfig to set up the options
  -l, --indent-level                Initial indentation level [0]
  -p, --preserve-newlines           Preserve line-breaks (--no-preserve-newlines disables)
  -m, --max-preserve-newlines       Number of line-breaks to be preserved in one chunk [10]
  -P, --space-in-paren              Add padding spaces within paren, ie. f( a, b )
  -E, --space-in-empty-paren        Add a single space inside empty paren, ie. f( )
  -j, --jslint-happy                Enable jslint-stricter mode
  -a, --space-after-anon-function   Add a space before an anonymous function's parens, ie. function ()
  --space-after-named-function      Add a space before a named function's parens, i.e. function example ()
  -b, --brace-style                 [collapse|expand|end-expand|none][,preserve-inline] [collapse,preserve-inline]
  -u, --unindent-chained-methods    Don't indent chained method calls
  -B, --break-chained-methods       Break chained method calls across subsequent lines
  -k, --keep-array-indentation      Preserve array indentation
  -x, --unescape-strings            Decode printable characters encoded in xNN notation
  -w, --wrap-line-length            Wrap lines that exceed N characters [0]
  -X, --e4x                         Pass E4X xml literals through untouched
  --good-stuff                      Warm the cockles of Crockford's heart
  -C, --comma-first                 Put commas at the beginning of new line instead of end
  -O, --operator-position           Set operator position (before-newline|after-newline|preserve-newline) [before-newline]
  --indent-empty-lines              Keep indentation on empty lines
  --templating                      List of templating languages (auto,django,erb,handlebars,php,smarty,angular) ["auto"] auto = none in JavaScript, all in HTML

Which correspond to the underscored option keys for both library interfaces

defaults per CLI options

{
    "indent_size": 4,
    "indent_char": " ",
    "indent_with_tabs": false,
    "editorconfig": false,
    "eol": "\n",
    "end_with_newline": false,
    "indent_level": 0,
    "preserve_newlines": true,
    "max_preserve_newlines": 10,
    "space_in_paren": false,
    "space_in_empty_paren": false,
    "jslint_happy": false,
    "space_after_anon_function": false,
    "space_after_named_function": false,
    "brace_style": "collapse",
    "unindent_chained_methods": false,
    "break_chained_methods": false,
    "keep_array_indentation": false,
    "unescape_strings": false,
    "wrap_line_length": 0,
    "e4x": false,
    "comma_first": false,
    "operator_position": "before-newline",
    "indent_empty_lines": false,
    "templating": ["auto"]
}

defaults not exposed in the cli

{
  "eval_code": false,
  "space_before_conditional": true
}

Notice not all defaults are exposed via the CLI. Historically, the Python and JS APIs have not been 100% identical. There are still a few other additional cases keeping us from 100% API-compatibility.

Loading settings from environment or .jsbeautifyrc (JavaScript-Only)

In addition to CLI arguments, you may pass config to the JS executable via:

any jsbeautify_-prefixed environment variables
a JSON-formatted file indicated by the --config parameter
a .jsbeautifyrc file containing JSON data at any level of the filesystem above $PWD

Configuration sources provided earlier in this stack will override later ones.

Setting inheritance and Language-specific overrides

The settings are a shallow tree whose values are inherited for all languages, but can be overridden. This works for settings passed directly to the API in either implementation. In the JavaScript implementation, settings loaded from a config file, such as .jsbeautifyrc, can also use inheritance/overriding.

Below is an example configuration tree showing all the supported locations for language override nodes. We'll use indent_size to discuss how this configuration would behave, but any number of settings can be inherited or overridden:

{
    "indent_size": 4,
    "html": {
        "end_with_newline": true,
        "js": {
            "indent_size": 2
        },
        "css": {
            "indent_size": 2
        }
    },
    "css": {
        "indent_size": 1
    },
    "js": {
       "preserve-newlines": true
    }
}

Using the above example would have the following result:

HTML files
- Inherit indent_size of 4 spaces from the top-level setting.
- The files would also end with a newline.
- JavaScript and CSS inside HTML
  - Inherit the HTML end_with_newline setting.
  - Override their indentation to 2 spaces.
CSS files
- Override the top-level setting to an indent_size of 1 space.
JavaScript files
- Inherit indent_size of 4 spaces from the top-level setting.
- Set preserve-newlines to true.

CSS & HTML

In addition to the js-beautify executable, css-beautify and html-beautify are also provided as an easy interface into those scripts. Alternatively, js-beautify --css or js-beautify --html will accomplish the same thing, respectively.

// Programmatic access
var beautify_js = require('js-beautify'); // also available under "js" export
var beautify_css = require('js-beautify').css;
var beautify_html = require('js-beautify').html;

// All methods accept two arguments, the string to be beautified, and an options object.

The CSS & HTML beautifiers are much simpler in scope, and possess far fewer options.

CSS Beautifier Options:
  -s, --indent-size                  Indentation size [4]
  -c, --indent-char                  Indentation character [" "]
  -t, --indent-with-tabs             Indent with tabs, overrides -s and -c
  -e, --eol                          Character(s) to use as line terminators. (default newline - "\\n")
  -n, --end-with-newline             End output with newline
  -b, --brace-style                  [collapse|expand] ["collapse"]
  -L, --selector-separator-newline   Add a newline between multiple selectors
  -N, --newline-between-rules        Add a newline between CSS rules
  --indent-empty-lines               Keep indentation on empty lines

HTML Beautifier Options:
  -s, --indent-size                  Indentation size [4]
  -c, --indent-char                  Indentation character [" "]
  -t, --indent-with-tabs             Indent with tabs, overrides -s and -c
  -e, --eol                          Character(s) to use as line terminators. (default newline - "\\n")
  -n, --end-with-newline             End output with newline
  -p, --preserve-newlines            Preserve existing line-breaks (--no-preserve-newlines disables)
  -m, --max-preserve-newlines        Maximum number of line-breaks to be preserved in one chunk [10]
  -I, --indent-inner-html            Indent <head> and <body> sections. Default is false.
  -b, --brace-style                  [collapse-preserve-inline|collapse|expand|end-expand|none] ["collapse"]
  -S, --indent-scripts               [keep|separate|normal] ["normal"]
  -w, --wrap-line-length             Maximum characters per line (0 disables) [250]
  -A, --wrap-attributes              Wrap attributes to new lines [auto|force|force-aligned|force-expand-multiline|aligned-multiple|preserve|preserve-aligned] ["auto"]
  -M, --wrap-attributes-min-attrs    Minimum number of html tag attributes for force wrap attribute options [2]
  -i, --wrap-attributes-indent-size  Indent wrapped attributes to after N characters [indent-size] (ignored if wrap-attributes is "aligned")
  -d, --inline                       List of tags to be considered inline tags
  --inline_custom_elements           Inline custom elements [true]
  -U, --unformatted                  List of tags (defaults to inline) that should not be reformatted
  -T, --content_unformatted          List of tags (defaults to pre) whose content should not be reformatted
  -E, --extra_liners                 List of tags (defaults to [head,body,/html] that should have an extra newline before them.
  --editorconfig                     Use EditorConfig to set up the options
  --indent_scripts                   Sets indent level inside script tags ("normal", "keep", "separate")
  --unformatted_content_delimiter    Keep text content together between this string [""]
  --indent-empty-lines               Keep indentation on empty lines
  --templating                       List of templating languages (auto,none,django,erb,handlebars,php,smarty,angular) ["auto"] auto = none in JavaScript, all in html

Directives

Directives let you control the behavior of the Beautifier from within your source files. Directives are placed in comments inside the file. Directives are in the format /* beautify {name}:{value} */ in CSS and JavaScript. In HTML they are formatted as .

Ignore directive

The ignore directive makes the beautifier completely ignore part of a file, treating it as literal text that is not parsed. The input below will remain unchanged after beautification:

// Use ignore when the content is not parsable in the current language, JavaScript in this case.
var a =  1;
/* beautify ignore:start */
 {This is some strange{template language{using open-braces?
/* beautify ignore:end */

Preserve directive

NOTE: this directive only works in HTML and JavaScript, not CSS.

The preserve directive makes the Beautifier parse and then keep the existing formatting of a section of code.

The input below will remain unchanged after beautification:

// Use preserve when the content is valid syntax in the current language, JavaScript in this case.
// This will parse the code and preserve the existing formatting.
/* beautify preserve:start */
{
    browserName: 'internet explorer',
    platform:    'Windows 7',
    version:     '8'
}
/* beautify preserve:end */

License

You are free to use this in any way you want, in case you find this useful or working for you but you must keep the copyright notice and license. (MIT)

Credits

Created by Einar Lielmanis, einar@beautifier.io
Python version flourished by Stefano Sanfilippo a.little.coder@gmail.com
Command-line for node.js by Daniel Stockman daniel.stockman@gmail.com
Maintained and expanded by Liam Newman bitwiseman@beautifier.io

Thanks also to Jason Diamond, Patrick Hof, Nochum Sossonko, Andreas Schneider, Dave Vasilevsky, Vital Batmanov, Ron Baldwin, Gabriel Harrison, Chris J. Shull, Mathias Bynens, Vittorio Gambaletta and others.

(README.md: js-beautify@1.15.1)

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Quick Overview

Pros

Cons

Code Examples

Getting Started

Competitor Comparisons

Pros of Prettier

Cons of Prettier

Code Comparison

Key Differences

Use Cases

Pros of Terser

Cons of Terser

Code Comparison

Key Differences

Use Cases

Community and Ecosystem

Pros of UglifyJS

Cons of UglifyJS

Code comparison

Key differences

Pros of Standard

Cons of Standard

Code Comparison

Key Differences

Pros of ESLint

Cons of ESLint

Code Comparison

Key Differences

Use Cases

Convert designs to code with AI

README

Contributors Needed

Installation

Node.js JavaScript

Node.js JavaScript (vNext)

Web Library

Python

Usage

Web Browser

Web Library

Node.js JavaScript

Python

Options

Loading settings from environment or .jsbeautifyrc (JavaScript-Only)

Setting inheritance and Language-specific overrides

CSS & HTML

Directives

Ignore directive

Preserve directive

License

Credits

Top Related Projects

Convert designs to code with AI

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