Node.js Library

Use js-beautify as a Node.js library to format JavaScript, CSS, and HTML programmatically.

Installation

npm install js-beautify

Importing

Choose between CommonJS require and ESM import depending on your project setup.

CommonJS

// Default export beautifies JavaScript
var beautify = require('js-beautify');

// Named exports for each language
var beautify_js   = require('js-beautify').js;
var beautify_css  = require('js-beautify').css;
var beautify_html = require('js-beautify').html;

// Subpath imports are also supported
var beautify_js = require('js-beautify/js').js;

API

All three beautifier methods share the same signature:

beautify(code, options)

Parameter	Type	Description
code	string	The source code string to beautify
options	object	Configuration options (optional)

Option names match the CLI flag names with hyphens replaced by underscores. For example, --indent-size 2 --space-in-empty-paren becomes { indent_size: 2, space_in_empty_paren: true }.

Examples

JavaScript

var beautify = require('js-beautify');

var ugly = 'function foo(a,b){return a+b;}';
var result = beautify(ugly, { indent_size: 2 });

console.log(result);
// function foo(a, b) {
//   return a + b;
// }

You can also read from a file:

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

CSS

var beautify_css = require('js-beautify').css;

var ugly = '.foo{color:red;background:blue;}';
var result = beautify_css(ugly, { indent_size: 2 });

console.log(result);
// .foo {
//   color: red;
//   background: blue;
// }

HTML

var beautify_html = require('js-beautify').html;

var ugly = '<div><p>Hello <strong>world</strong></p></div>';
var result = beautify_html(ugly, { indent_size: 2 });

console.log(result);
// <div>
//   <p>Hello <strong>world</strong></p>
// </div>

Legacy Aliases

The following legacy aliases exist for backwards compatibility. Prefer the shorter .js, .css, and .html names in new code.

var beautify = require('js-beautify');

// These are equivalent to .js, .css, and .html respectively
beautify.js_beautify(code, options);
beautify.css_beautify(code, options);
beautify.html_beautify(code, options);

Common Options

Option	Default	Description
indent_size	4	Number of spaces per indentation level
indent_char	" "	Character used for indentation
indent_with_tabs	false	Use tabs instead of spaces
eol	"auto"	End-of-line character(s) (auto = detect from file, else \n)
end_with_newline	false	Ensure the output ends with a newline
preserve_newlines	true	Preserve existing blank lines
max_preserve_newlines	10	Maximum consecutive blank lines to keep
brace_style	"collapse"	Brace placement style (collapse, expand, end-expand, none)
wrap_line_length	0	Wrap lines longer than N characters (0 = disabled)