js_beautify() / beautify.js()

Beautify and reformat JavaScript source code using the js-beautify Node.js API.

Overview

The default export of js-beautify is a function that beautifies JavaScript source code. All three aliases below are equivalent:

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

For ESM imports:

import beautify from 'js-beautify';

beautify.js(code, options);

Function signature

beautify(sourceCode: string, options?: object): string

Parameters

sourceCode · string · required

The JavaScript source code string to beautify. You can also pass minified code, bookmarklets, or scripts packed by Dean Edward’s packer.

options · object

Configuration options object. All keys use underscores (e.g., indent_size). Options loaded from .jsbeautifyrc or environment variables are merged with lower priority than options passed directly here.

Show options

indent_size · number · default: "4"

Number of spaces per indentation level.

indent_char · string · default: " "

Character used for indentation. Overridden to \t when indent_with_tabs is true.

indent_with_tabs · boolean · default: "false"

Indent with tabs instead of spaces. When true, sets indent_char to \t.

eol · string · default: "auto"

Line terminator character(s). auto uses the first newline found in the input file, or \n if none is found. Accepts \n, \r\n, or \r.

end_with_newline · boolean · default: "false"

Ensure the output ends with a newline character.

indent_level · number · default: "0"

Initial indentation level applied to all output lines. Useful when embedding code inside a larger formatted document.

preserve_newlines · boolean · default: "true"

Preserve existing blank lines in the source. Disable to remove all extra blank lines.

max_preserve_newlines · number · default: "10"

Maximum number of consecutive blank lines to preserve in a single run. Only applies when preserve_newlines is true.

space_in_paren · boolean · default: "false"

Add padding spaces inside parentheses, e.g. f( a, b ) instead of f(a, b).

space_in_empty_paren · boolean · default: "false"

Add a single space inside empty parentheses, e.g. f( ) instead of f().

jslint_happy · boolean · default: "false"

Enable stricter JSLint-compatible output. Implies space_after_anon_function: true.

space_after_anon_function · boolean · default: "false"

Add a space before an anonymous function’s parentheses, e.g. function () instead of function().

space_after_named_function · boolean · default: "false"

Add a space before a named function’s parentheses, e.g. function example () instead of function example().

brace_style · string · default: "collapse"

Controls brace placement. Accepted values: collapse, expand, end-expand, none. Append ,preserve-inline to any value to keep single-line blocks on one line (e.g., collapse,preserve-inline).

unindent_chained_methods · boolean · default: "false"

Do not indent chained method calls relative to their receiver.

break_chained_methods · boolean · default: "false"

Break chained method calls onto separate lines.

keep_array_indentation · boolean · default: "false"

Preserve the original indentation of array elements rather than re-indenting them.

unescape_strings · boolean · default: "false"

Decode printable characters encoded in \xNN hexadecimal notation back to their literal characters.

wrap_line_length · number · default: "0"

Wrap lines that exceed this many characters. Set to 0 to disable wrapping.

e4x · boolean · default: "false"

Pass E4X XML literals through untouched instead of attempting to parse them as JavaScript.

comma_first · boolean · default: "false"

Place commas at the beginning of new lines instead of at the end.

operator_position · string · default: "before-newline"

Controls where binary operators are placed when a line is wrapped. Accepted values: before-newline, after-newline, preserve-newline.

indent_empty_lines · boolean · default: "false"

Keep indentation whitespace on otherwise empty lines.

templating · array · default: "[\"auto\"]"

List of templating languages to recognize and pass through. Accepted values: auto, none, django, erb, handlebars, php, smarty, angular. auto disables all templating in JavaScript context.

eval_code · boolean · default: "false"

Evaluate the code using a JS interpreter before beautifying. May help with some obfuscated scripts, but poses a security risk. Not exposed via CLI.

space_before_conditional · boolean · default: "true"

Add a space before conditional expressions such as if (. Not exposed via CLI.

Return value

result · string

The beautified JavaScript source code as a string.

Examples

CommonJS

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

const ugly = 'function hello(name){return "Hello, "+name;}';

const pretty = beautify(ugly, {
  indent_size: 2,
  space_in_empty_paren: true,
});

console.log(pretty);
// function hello(name) {
//   return "Hello, " + name;
// }

Configuration option names are the same as CLI flag names but with underscores instead of dashes. For example, --indent-size 2 maps to { indent_size: 2 }.

Configuration loading (Node.js only)

In the Node.js environment, options are resolved from the following sources in priority order (highest to lowest):

1. Options passed directly to the function
2. jsbeautify_-prefixed environment variables
3. A JSON config file specified via --config
4. A .jsbeautifyrc JSON file found at or above the current working directory

Language-specific overrides

When loading from .jsbeautifyrc, you can scope settings to a specific language using a nested key:

{
  "indent_size": 4,
  "js": {
    "preserve_newlines": true
  },
  "css": {
    "indent_size": 2
  }
}