ECMAScript code beautifier/formatter

npm install esformatter
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Build Status

ECMAScript code beautifier/formatter.


This tool is still on early development and is missing support for many important features.

We are looking for contributors!!

Why? doesn't have enough options and not all IDEs/Editors have a good JavaScript code formatter. I would like to have a command line tool (and standalone lib) as powerful/flexible as the WebStorm and FDT code formatters.

This tool could also be reused by other node.js libs like escodegen to format the output (so each lib has a single responsibility).

For more reasoning behind it and history of the project see: esformatter & rocambole


This tool uses rocambole (based on Esprima) to recursively parse the tokens and transform it in place.


  • granular control about white spaces, indent and line breaks.
  • command line interface (cli).
  • be non-destructive.
  • option to control automatic semicolon insertion (asi).
  • support for local/global config file so settings can be shared between team members.
  • presets for the most popular style guides (Google, jQuery, Idiomatic.js).
  • be the best JavaScript code formatter.


esformatter.format(str[, opts]):String

So far esformatter exposes 2 methods.

format() method which receives a string containing the code that you would like to format and the configuration options that you would like to use and returns a string with the result.

var esformatter = require('esformatter');

// for a list of available options check "lib/preset/default.json"
var options = {
    // inherit from the default preset
    preset : 'default',
    indent : {
        value : '  '
    lineBreak : {
        before : {
            // at least one line break before BlockStatement
            BlockStatement : '>=1',
            // only one line break before BlockStatement
            DoWhileStatementOpeningBrace : 1,
            // ...
    whiteSpace : {
        // ...

var fs = require('fs');
var codeStr = fs.readFileSync('path/to/js/file.js').toString();

// return a string with the formatted code
var formattedCode = esformatter.format(codeStr, options);

esformatter.transform(ast[, opts]):AST

or you can use the transform() method to manipulate an AST in place (allows pipping other tools that manipulates the AST). - so far only supports rocambole generated ASTs, but we will work to fix this limitation in the future (see issue #86).

var inputAST = rocambole.parse('var foo=123;');
// you can also pass the formatting options as second argument like the
// `format` method
var outputAST = esformatter.transform(inputAST);
assert(outputAST === inputAST, 'edits AST in place');
assert(outputAST.toString() === 'var foo = 123;', 'formats input');


You can also use the simple command line interface to process stdin and stdout or read from a file.

npm install -g esformatter


esformatter [OPTIONS] [FILES]

  -c, --config   Path to custom configuration file.
  -p, --preset   Set style guide preset ("jquery", "default").
  -h, --help     Display help and usage details.
  -v, --version  Display the current version.


# format "test.js" and output result to stdout
esformatter test.js
# you can also pipe other shell commands (read file from stdin)
cat test.js | esformatter
# format "test.js" using options in "options.json" and output result to stdout
esformatter --config options.json test.js
# process "test.js" and writes to "test.out.js"
esformatter test.js > test.out.js
# you can override the default settings, see lib/preset/default.json for
# a list of available options
esformatter test.js --indent.value="\t" --lineBreak.before.IfStatementOpeningBrace=0


esformatter will look for the closest .esformatter file and use that as a setting unless you specify --preset or --config.

You also have the option to put your esformatter settings inside the package.json file under the esformatter property.

Settings from multiple files will be merged until it finds a config file that contains the property "preset" or "root": true; that makes it easy to define exceptions to the project rules without needing to copy all the shared properties. - for an example see test files inside the "test/compare/rc" folder.

The "preset" property is used to set the prototype of the config file, enabling inheritance. For instance, you can say your config inherits from the jquery preset and only override the settings you need:

  "preset": "jquery",
  "indent": {
    "value": "  "

PS: the jQuery preset is still under development.


We have an IRC channel #esformatter on for quick discussions about the project development/structure.

Project structure / Contributing


Projects built on top of esformatter


Released under the MIT license

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