Webpack Prefetch Chunk Plugin

This plugin provides a helper function for prefetching chunks dynamically whenever you want.

You might know the import(/* webpackPrefetch: true */ 'MyModule'); syntax (see documentation). Using that magic comment, the chunk containing MyModule will be prefetched as soon as the chunk containing the import(...) statement is installed. There are use cases where this is too early and unflexible.

Example use case

Consider the following setup for vue-router (this plugin works for any async chunks, vue-router is just an example):

const PageA = () => import(/* webpackChunkName: "page-a" */'./PageA.vue')
const PageB = () => import(/* webpackChunkName: "page-b" */'./PageB.vue')
const PageC = () => import(/* webpackChunkName: "page-c" */'./PageC.vue')

const router = new VueRouter({
  routes: [
    { path: '/a', component: PageA },
    { path: '/b', component: PageB },
    { path: '/c', component: PageC },
  ]
})

Adding /* webpackPrefetch: true */ to any of the above import(...)s will prefetch that chunk directly when the router is being set up. You might end up prefetching a lot of stuff unnecessarily, thereby wasting your user's bandwidth.

Assume we want to prefetch page-b only when the user accesses /a. To do so, we call __webpack_require__.pfc('page-b') somewhere in PageA.vue, for example in the mounted hook.

Real-world use case: A login form. When the user submits the form then a tiny request to your API is made to check the credentials and additionally a large request to load the chunk that renders a dashboard (first page after login). You could prefetch that chunk as soon as the user starts typing something into the login form. Just call __webpack_require__.pfc('chunk-with-dashboard') from the change handler for the input fields.

Install

yarn add webpack-prefetch-chunk

or

npm install webpack-prefetch-chunk

Usage

const PrefetchChunkPlugin = require('webpack-prefetch-chunk');

module.exports = {
    plugins: [
        new PrefetchChunkPlugin()
    ]
};

The plugin adds a __webpack_require__.pfc function to the manifest (pfc = prefetch chunk). Call that function in any module you wish. Pass it the name of the chunk you want to load, i.e. the name specified with /* webpackChunkName: "my-chunk-name" */.

At runtime, a <link rel="prefetch" as="script" href="..."> element is appended to the document head. Nothing is done if the chunk is already loaded or is currently loading/prefetching.

The implementation is inspired by webpack itself. The rest of the code is to ensure that the helper function can be used regardless of the optimization.namedChunks setting.

Using Typescript?

Add the following to a .d.ts file somewhere in your include path specified in tsconfig.json:

declare global {
    const __webpack_require__: {
        pfc(chunkId: string): void,
    }
}