watchify

What is watchify?

Watchify is a browserify plugin that enables fast incremental bundling. It watches your files and updates the bundle whenever any of the source files change, making it ideal for development environments where quick feedback is essential.

What are watchify's main functionalities?

Incremental Bundling

This feature allows you to set up a watch on your files so that any changes trigger a rebundling process. The code sample demonstrates how to use watchify with browserify to watch for changes in 'main.js' and update 'bundle.js' accordingly.

const watchify = require('watchify');
const browserify = require('browserify');
const fs = require('fs');

const b = browserify({
  entries: ['main.js'],
  cache: {},
  packageCache: {},
  plugin: [watchify]
});

b.on('update', bundle);
bundle();

function bundle() {
  b.bundle().pipe(fs.createWriteStream('bundle.js'));
}

Custom Watch Options

Watchify allows you to customize the watch options, such as setting a delay before rebundling. The code sample shows how to set a custom delay of 1000 milliseconds before the rebundling process starts.

const watchify = require('watchify');
const browserify = require('browserify');
const fs = require('fs');

const customOpts = {
  entries: ['main.js'],
  cache: {},
  packageCache: {},
  plugin: [watchify],
  delay: 1000 // Custom delay before rebundling
};

const b = browserify(customOpts);

b.on('update', bundle);
bundle();

function bundle() {
  b.bundle().pipe(fs.createWriteStream('bundle.js'));
}

Other packages similar to watchify

gulp-watch

Gulp-watch is a file watcher specifically designed for use with Gulp. It allows you to watch files and run Gulp tasks when changes are detected. Unlike watchify, which is tightly integrated with browserify, gulp-watch is more general-purpose and can be used with any Gulp task.

chokidar

Chokidar is a highly efficient file watcher that can be used to watch files and directories for changes. It is more flexible than watchify as it is not tied to any specific bundler and can be used in a variety of scenarios. However, it requires more setup to achieve the same functionality as watchify when used with browserify.

webpack

Webpack is a powerful module bundler that includes built-in file watching capabilities. It can be configured to watch files and recompile the bundle when changes are detected. While it offers more features and flexibility compared to watchify, it also comes with a steeper learning curve.

README

watchify

watch mode for browserify builds

Update any source file and your browserify bundle will be recompiled on the spot.

example

$ watchify main.js -o static/bundle.js

Now as you update files, static/bundle.js will be automatically incrementally rebuilt on the fly.

The -o option can be a file or a shell command (not available on Windows) that receives piped input:

watchify main.js -o 'exorcist static/bundle.js.map > static/bundle.js' -d

watchify main.js -o 'uglifyjs -cm > static/bundle.min.js'

You can use -v to get more verbose output to show when a file was written and how long the bundling took (in seconds):

$ watchify browser.js -d -o static/bundle.js -v
610598 bytes written to static/bundle.js (0.23 seconds) at 8:31:25 PM
610606 bytes written to static/bundle.js (0.10 seconds) at 8:45:59 PM
610597 bytes written to static/bundle.js (0.14 seconds) at 8:46:02 PM
610606 bytes written to static/bundle.js (0.08 seconds) at 8:50:13 PM
610597 bytes written to static/bundle.js (0.08 seconds) at 8:58:16 PM
610597 bytes written to static/bundle.js (0.19 seconds) at 9:10:45 PM

usage

Use watchify with all the same options as browserify except that -o (or --outfile) is mandatory. Additionally, there are also:

Standard Options:

  --outfile=FILE, -o FILE

    This option is required. Write the browserify bundle to this file. If
    the file contains the operators `|` or `>`, it will be treated as a
    shell command, and the output will be piped to it.

  --verbose, -v                     [default: false]

    Show when a file was written and how long the bundling took (in
    seconds).

  --version

    Show the watchify and browserify versions with their module paths.

Advanced Options:

  --delay                           [default: 100]

    Amount of time in milliseconds to wait before emitting an "update"
    event after a change.

  --ignore-watch=GLOB, --iw GLOB    [default: false]

    Ignore monitoring files for changes that match the pattern. Omitting
    the pattern will default to "**/node_modules/**".

  --poll=INTERVAL                   [default: false]

    Use polling to monitor for changes. Omitting the interval will default
    to 100ms. This option is useful if you're watching an NFS volume.

methods

var watchify = require('watchify');

watchify(b, opts)

watchify is a browserify plugin, so it can be applied like any other plugin. However, when creating the browserify instance b, you MUST set the cache and packageCache properties:

var b = browserify({ cache: {}, packageCache: {} });
b.plugin(watchify);

var b = browserify({
  cache: {},
  packageCache: {},
  plugin: [watchify]
});

By default, watchify doesn't display any output, see events for more info.

b continues to behave like a browserify instance except that it caches file contents and emits an 'update' event when a file changes. You should call b.bundle() after the 'update' event fires to generate a new bundle. Calling b.bundle() extra times past the first time will be much faster due to caching.

Important: Watchify will not emit 'update' events until you've called b.bundle() once and completely drained the stream it returns.

var fs = require('fs');
var browserify = require('browserify');
var watchify = require('watchify');

var b = browserify({
  entries: ['path/to/entry.js'],
  cache: {},
  packageCache: {},
  plugin: [watchify]
});

b.on('update', bundle);
bundle();

function bundle() {
  b.bundle()
    .on('error', console.error)
    .pipe(fs.createWriteStream('output.js'))
  ;
}

options

You can to pass an additional options object as a second parameter of watchify. Its properties are:

opts.delay is the amount of time in milliseconds to wait before emitting an "update" event after a change. Defaults to 100.

opts.ignoreWatch ignores monitoring files for changes. If set to true, then **/node_modules/** will be ignored. For other possible values see Chokidar's documentation on "ignored".

opts.poll enables polling to monitor for changes. If set to true, then a polling interval of 100ms is used. If set to a number, then that amount of milliseconds will be the polling interval. For more info see Chokidar's documentation on "usePolling" and "interval". This option is useful if you're watching an NFS volume.

var b = browserify({ cache: {}, packageCache: {} });
// watchify defaults:
b.plugin(watchify, {
  delay: 100,
  ignoreWatch: ['**/node_modules/**'],
  poll: false
});

b.close()

Close all the open watch handles.

events

b.on('update', function (ids) {})

When the bundle changes, emit the array of bundle ids that changed.

b.on('bytes', function (bytes) {})

When a bundle is generated, this event fires with the number of bytes.

b.on('time', function (time) {})

When a bundle is generated, this event fires with the time it took to create the bundle in milliseconds.

b.on('log', function (msg) {})

This event fires after a bundle was created with messages of the form:

X bytes written (Y seconds)

with the number of bytes in the bundle X and the time in seconds Y.

working with browserify transforms

If your custom transform for browserify adds new files to the bundle in a non-standard way without requiring. You can inform Watchify about these files by emiting a 'file' event.

module.exports = function(file) {
  return through(
    function(buf, enc, next) {
      /*
        manipulating file content
      */
      
      this.emit("file", absolutePathToFileThatHasToBeWatched);
      
      next();
    }
  );
};

install

With npm do:

$ npm install -g watchify

to get the watchify command and:

$ npm install watchify

to get just the library.

troubleshooting

rebuilds on OS X never trigger

It may be related to a bug in fsevents (see #250 and stackoverflow). Try the --poll flag and/or renaming the project's directory - that might help.

watchify swallows errors

To ensure errors are reported you have to add a event listener to your bundle stream. For more information see (browserify/browserify#1487 (comment) and stackoverflow)

Example:

var b = browserify();
b.bundle()
  .on('error', console.error)
   ...
;

see also

• budo – a simple development server built on watchify
• errorify – a plugin to add error handling to watchify development
• watchify-request – wraps a watchify instance to avoid stale bundles in HTTP requests
• watchify-middleware – similar to watchify-request, but includes some higher-level features

license

MIT