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The API mirrors the CLI except you must provide a stream for logging, and it provides a couple extra options.

b = budo([entry], [opts])

Sets up a new instance of budo, where entry is a path or or array of paths.

entry can be optional -- if no entry paths are given, budo simply acts as a static HTTP server with optional LiveReload.

The return value is an event emitter.


var budo = require('budo')
var babelify = require('babelify')

budo('./src/index.js', {
  live: true,             // live reload
  stream: process.stdout, // log to stdout
  port: 8000,             // use this as the base port
  browserify: {
    transform: babelify   // use ES6
}).on('connect', function(ev) {


All settings are optional.

  • port (Number)
    • the base port to use for the development server (default 9966)
  • livePort (Number)
    • the base port to use for the LiveReload server (default 35729)
  • portfind (Boolean)
    • whether to use portfinding to find the next available ports (default true)
  • host (String)
    • the host to listen on (default 'localhost')
  • live (Boolean|String|Object)
    • whether to set up a default LiveReload integration (see LiveReload)
    • if a string is specified, only filenames matching that glob will trigger LiveReload events
    • object will be passed along to the live() function
  • cors (Boolean)
    • Set the header to use CORS (Access-Control-Allow-Origin: *)
  • ssl (Boolean)
    • Creates an HTTPS server instead of HTTP
  • cert (String)
    • The SSL public certificate file path (default 'cert.pem')
  • key (String)
    • The SSL private key file path (default 'key.pem')
  • watchGlob (Array|String)
    • a glob string or array of glob strings to use as the default when is specified, or when live() is called without arguments
    • defaults to '**/*.{html,css}'
  • open (Boolean)
    • whether to launch the browser (default false)
  • dir (String|Array)
    • a folder or list of folders to use as the base path for static assets (default process.cwd())
    • a default index.html will be searched in the first dir folder
  • stream (writable stream)
    • a writable stream like process.stdout for ndjson logging (default undefined)
  • debug (Boolean)
    • whether to enable source maps from browserify (default true)
  • serve (String)
    • if specified, the <script src> will use this path; defaults to first entry filename
  • title (String)
    • an optional <title> to use for the default index.html
  • css (String)
    • an optional <link href> stylesheet URL to use for the default index.html
  • browserify (Object)
    • an object of options passed to browserify
  • browserifyArgs (Array)
    • an array of command-line arguments passed to browserify
    • if specified, this will be used to construct the new instance
  • middleware (Array|Function)
    • an optional function or array of fn(req, res, next) functions for the server which is run before other routes; using connect style middleware
  • errorHandler (Boolean|Function)
    • whether to include a DOM-based reporter build/syntax errors (default true)
    • can be a reporter(err) function which takes an Error and returns the new bundle contents
  • forceDefaultIndex (Boolean)
    • whether to always generate index.html instead of serving a static file, if one is present (default: false)
  • pushstate (Boolean)
    • enable push state support, which defaults 404 routes to the index (default false)
    • Recommended you also add something like <base href="/"> to your HTML <head>
  • base (Boolean|String)
    • add <base href="/"> to the generated default HTML page if set to true, or uses the specified path if it's a string
  • verbose (Boolean)
    • also print 'debug' level messages to garnish; such as the pending state of the bundle and how many files changed in the last update.
  • defaultIndex (Function)
    • a function fn(params, req) that returns a Readable stream, takes the following params:
      { entry: opts.serve, title: opts.title, css: opts.css }
    • defaults to simple-html-index
  • staticOptions (Object)
    • an object passed to serve-static options
    • this object is merged with the default options: { cacheControl: false }

b = budo.cli(args[, opts])

Runs budo as a command-line tool, from the specified array of arguments and an optional opts object for overrides. The options are the same as above.

This method returns the budo instance, or null if the args command includes --version or --help.

For example, running the following script from the command line would behave like budo, but with some added features by default:

var args = process.argv.slice(2)
var babelify = require('babelify')

var budo = require('budo').cli(args, {
  // additional overrides for our custom tool
  pushstate: true,
  browserify: {
    transform: babelify

Note: In the CLI, anything after -- gets passed to opts.browserifyArgs. Whenever opts.browserifyArgs is specified, browserify will be created with browserify/bin/args instead of its usual constructor.


Closes the budo instance and its associated server/watcher/etc.


If live reload is enabled (i.e. through or live()), this will send a LiveReload event to the given path and then trigger the "reload" event.

If path is undefined, this is treated as a hard page reload.[opt])

If live was not specified, you can manually enable the LiveReload server with the specified opt options:

  • plugin if true, the HTML will not have the LiveReload script injected into it, default false
  • path the script URL for the LiveReload client, defaults to '/budo/livereload.js'
  • include a path or array of paths to files that should be added to the LiveReload client, defaults to an empty array
  • cache whether to cache the LiveReload client file (faster) or re-bundle it on each request (easier to develop LiveReload clients), default true
  • debug whether to add source maps to the bundled LiveReload client, default false
  • expose whether to expose require('budo-livereload') on the global context, default false

See LiveReload for details.[globs, chokidarOpts])

If live was not specified, you can manually enabe chokidar's file watching with the specified globs (array or string) and options.

globs defaults to watching **/*.{html,css}.

See LiveReload for details.


b.on('exit', fn)

Called when the server is closed.

b.on('error', fn)

Called on a fatal error, like not being able to create the server.

b.on('connect', fn)

Called once the budo server connects. The callback is passed an event object that looks like this:

  uri: 'http://localhost:9966/',  // served URI
  serve: 'bundle/entry%20file.js' // the URL path for our entry file
  dir: 'app',                     // the working directory being served
  host: 'localhost',              // defaults to localhost
  port: 9966,                     // the port we're running on
  entries: [ 'entry file.js' ],   // an array of entry file paths
  server: HTTPServer              // the HTTP/HTTPS server

Note: The dir field might be a string or array, depending on user input.

b.on('pending', fn)

Called when the source changes and begins the new incremental reload.

b.on('update', fn)

Called after the 'pending' event, once the bundle has finished reloading. It is passed the following:

fn(contents, changedDependencies)

Where contents is a Buffer with the new bundle source, and changedDependencies is an array of dependencies that were changed since last bundle. On the initial update, this array will be empty.

b.on('reload', fn)

Called after LiveReload has triggered a new event. The listener should have the signature fn(file), where file is the path being reloaded.

This is only called when is specified, or after b.reload(file) is manually called.

b.on('watch', fn)

Called after a file watch event with the signature: fn(event, file), where event could be "add", "change", "unlink", etc and file is the file path being changed.

If was not specified, and was never set up, this event will not get called.


custom CLI wrappers

If you use budo.cli() you can create a simple budo CLI wrapper with some pre-defined options and configurations, such as this dev.js script:

require('budo').cli(process.argv.slice(2), {
  port: 8080,
  open: true,
  live: true

Now you can run dev.js with regular budo CLI flags:

node dev.js src/index.js:bundle.js -- -t babelify

http server

A static HTTP server with no browserify capabilities, LiveReload integration, and a custom glob to watch for.

  live: true,
  watchGlob: '{src,examples}/**/*.{html,css,js}'


Using middleware to create a small non-static server. This can be an array of functions, or just a single function.

var url = require('url')

var app = budo('./app.js', {
  middleware: function (req, res, next) {
    if (url.parse(req.url).pathname === '/api') {
      res.statusCode = 200
      res.end('hello world')
    } else {
      // fall through to other routes

Folders Mapping to .html Files

Let's say your dev server should map localhost:9966/about and localhost:9966/about/ to an HTML file called localhost:9966/about.html. You can specify options to the underlying static middleware and remove trailing slashes like so:

// dev.js
var slashes = require('connect-slashes')

require('budo').cli(process.argv.slice(2), {
  middleware: slashes(false),
  staticOptions: {
    index: false,
    extensions: [ 'html', 'htm' ]

Now you can run the above dev.js file just like you would budo:

node dev.js src/index.js:bundle.js --live -- -t babelify

configure browserify

If you need more control over the bundler, such as adding external(), you can use a browserify plugin.

For example, to ignore large files when browserifying the unicode package, write a dev.js script like this:

require('budo').cli(process.argv.slice(2), {
  browserify: {
    plugin: bundler => bundler.ignore('unicode/category/So')

Now, you can call this dev.js script from node just like you would with budo CLI:

node dev.js src/index.js:bundle.js --live -- -t babelify

Here is a more complex example, where require('os-arch') returns the OS architecture of whatever machine is running budo.

const os = require('os');
const path = require('path');
const fromString = require('from2-string');

require('budo').cli(process.argv.slice(2), {
  browserify: {
    plugin: bundler => {
      // A "dynamic" module from Node.js
      // Keep in mind the result of the stream is cached by browserify!
      const moduleName = 'os-arch';

      // Give it a fake file name in node_modules
      const moduleFile = path.resolve(process.cwd(), 'node_modules', moduleName, `${moduleName}.js`);

      const message = os.arch();
      const stream = fromString(`module.exports = ${JSON.stringify(message)}`);
      bundler.require(stream, { file: moduleFile, expose: moduleName });

build tools

Budo doesn't need a Grunt or Gulp specific plugin to work. Instead, if you wish to use Grunt or Gulp, it is safer to require budo directly, and wrap it within your task runner:

var gulp = require('gulp')
var budo = require('budo')

//start our local development server
gulp.task('dev', function(cb) {
  budo('index.js', {
    stream: process.stdout
  }).on('connect', function(ev) {
      // do something on connect ...
    .on('exit', cb)

Now running gulp dev will spin up a server on 9966, spawn watchify, and incrementally rebundle during development. It will stub out an index.html and serve the browserified contents of index.js and write pretty-printed logs to stdout.