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(split-require
Bundle splitting for CommonJS and ES modules (dynamic import()) in browserify
Lazy load the parts of your app that are not immediately used, to make the
initial load faster.
This module works without a compile step on the server, and in the browser with
the browserify plugin.
NOTE: split-require v3+ works with browserify 16 and newer. If you are using
an older browserify version and can't upgrade, use split-require v2.
What? -
Install -
Usage -
Plugin CLI -
Plugin API -
License: MIT
What?
This plugin takes source files with splitRequire() calls like:
var html = require('choo/html')
var app = require('choo')()
var splitRequire = require('split-require')
app.route('/', mainView)
app.mount('body')
var component
function mainView () {
return html`<body>
${component ? component.render() : html`
<h1>Loading</h1>
`}
</body>`
}
splitRequire('./SomeComponent', function (err, SomeComponent) {
component = new SomeComponent()
app.emitter.emit('render')
})
And splits off splitRequire()d files into their own bundles, that will be
dynamically loaded at runtime.
In this case, a main bundle would be created including choo, choo/html and
the above file, and a second bundle would be created for the SomeComponent.js
file and its dependencies.
Install
npm install split-require
Usage
Use the split-require function for modules that should be split off into a separate bundle.
var splitRequire = require('split-require')
require('./something') // loaded immediately
splitRequire('./other', function () {}) // loaded async
This works out of the box in Node.js.
Add the browserify plugin as described below in order to make it work in the browser, too.
import()
You can use split-require with ES modules import() syntax using the
Babel plugin.
browserify app.js \
-t [ babelify --plugins dynamic-import-split-require ] \
-p split-require
import('./SomeComponent').then(function (SomeComponent) {
// Works!
console.log(SomeComponent)
})
! Note that this transform is not 100% spec compliant.
import()is an ES modules feature, not a CommonJS one.
In CommonJS with this plugin, the exports object is the value of the
module.exportsof the imported module, so it may well be a function or some
other non-object value. In ES modules, the exports object in.then()will
always be an object, with a.defaultproperty for default exports and other
properties for named exports. You'd never get a function back in.then()in
native ES modules.
Browserify Plugin CLI Usage
browserify ./entry -p [ split-require --out /output/directory ]
> /output/directory/bundle.js
Options
--out
Set the output for dynamic bundles. Use a folder path to place dynamic bundles
in that folder. You can also use outpipe
syntax: in that case use %f in place of the bundle name. For example:
-p [ split-require --out 'uglifyjs > /output/directory/%f' ]
The default is ./, outputting in the current working directory.
--public
Public path to load dynamic bundles from.
Defaults to ./, so dynamic bundle #1 is loaded as ./bundle.1.js.
--sri
Hash algorithm to use for subresource integrity. By default, subresource
integrity is not used.
When enabled, the runtime loader will add crossorigin and integrity
attributes to dynamically loaded bundles.
One of sha256, sha384, sha512.
Browserify Plugin API Usage
var splitRequire = require('split-require')
browserify('./entry')
.plugin(splitRequire, {
dir: '/output/directory'
})
.pipe(fs.createWriteStream('/output/directory/bundle.js'))
With factor-bundle
Through the API, split-require can also be used together with
factor-bundle. Listen for the
factor.pipeline event, and unshift the result of the createStream function
to the 'pack' label:
b.plugin(splitRequire, { dir: '/output/directory' })
b.plugin(factorBundle, { /* opts */ })
b.on('factor.pipeline', function (file, pipeline) {
var stream = splitRequire.createStream(b, {
dir: '/output/directory'
})
pipeline.get('pack').unshift(stream)
})
Note that you must pass the options to the plugin and the stream.
Other plugins that generate multiple outputs may need a similar treatment.
Options
dir
Set the folder to output dynamic bundles to. Defaults to ./.
This is only necessary if the output() option is not used.
filename(entry)
Function that generates a name for a dynamic bundle.
Receives the entry point row as the only parameter. The default is:
function filename (entry) {
return 'bundle.' + entry.index + '.js'
}
output(bundleName)
Function that should return a stream. The dynamic bundle will be written to the
stream. bundleName is the generated name for the dynamic bundle.
At runtime, the main bundle will attempt to use this name to load the bundle,
so it should be publically accessible under this name.
The bundleName can be changed by emitting a name event on the returned
stream before the stream finishes. This is useful to generate a bundle name
based on a hash of the file contents, for example.
var fs = require('fs')
var crypto = require('crypto')
var to = require('flush-write-stream')
b.plugin(splitRequire, {
output: function (bundleName) {
var stream = fs.createWriteStream('/tmp/' + bundleName)
var hash = crypto.createHash('sha1')
return to(onwrite, onend)
function onwrite (chunk, enc, cb) {
hash.update(chunk)
stream.write(chunk, cb)
}
function onend (cb) {
stream.end()
var name = hash.digest('hex').slice(0, 10) + '.js'
this.emit('name', name)
fs.rename('/tmp/' + bundleName, './' + name, cb)
}
}
})
public
Public path to load dynamic bundles from.
Defaults to ./, so dynamic bundle #1 is loaded as ./bundle.1.js.
sri
Hash algorithm to use for subresource integrity. By default, subresource
integrity is not used.
When enabled, the runtime loader will add crossorigin and integrity
attributes to dynamically loaded bundles.
One of sha256, sha384, sha512.
Events
b.on('split.pipeline', function (pipeline, entry, basename) {})
split-require emits an event on the browserify instance for each pipeline it
creates.
pipeline is a labeled-stream-splicer with labels:
'pack'- browser-pack'wrap'- apply final wrapping
entry is the browserify row object for the entry point of the dynamic bundle.
basename is the name of the dynamic bundle file.