Adding Lazy Loading documentation with examples (#2118)

README.md

@@ -407,6 +407,72 @@ end
 ```
 You can read more about this in the [Vue docs](https://vuejs.org/v2/guide/installation.html#CSP-environments).
 
+#### Lazy loading integration
+
+See [docs/es6](docs/es6.md) to know more about Webpack and Webpacker configuration.
+
+For instance, you can lazy load Vue JS components:
+
+Before:
+```js
+import Vue from 'vue'
+import { VCard } from 'vuetify/lib'
+
+Vue.component('VCard', VCard)
+```
+
+After:
+```js
+import Vue from 'vue'
+
+// With destructuring assignment
+Vue.component('VCard', import('vuetify/lib').then(({ VCard }) => VCard)
+
+// Or without destructuring assignment
+Vue.component('OtherComponent', () => import('./OtherComponent'))
+```
+
+You can use it in a Single File Component as well:
+
+```html
+<template>
+  ...
+</template>
+
+<script>
+export default {
+  components: {
+    OtherComponent: () => import('./OtherComponent')
+  }
+}
+</script>
+```
+
+By wrapping the import function into an arrow function, Vue will execute it only when it gets requested, loading the module in that moment.
+
+##### Automatic registration
+
+```js
+/**
+ * The following block of code may be used to automatically register your
+ * Vue components. It will recursively scan this directory for the Vue
+ * components and automatically register them with their "basename".
+ *
+ * Eg. ./components/OtherComponent.vue -> <other-component></other-component>
+ * Eg. ./UI/ButtonComponent.vue -> <button-component></button-component>
+ */
+
+const files = require.context('./', true, /\.vue$/i)
+files.keys().map(key => {
+  const component = key.split('/').pop().split('.')[0]
+
+  // With Lazy Loading
+  Vue.component(component, () => import(`${key}`))
+
+  // Or without Lazy Loading
+  Vue.component(component, files(key).default)
+})
+```
 
 ### Elm
 

docs/es6.md

@@ -1,6 +1,5 @@
 # ES6
 
-
 ## Babel
 
 Webpacker ships with [babel](https://babeljs.io/) - a JavaScript compiler so
@@ -26,6 +25,25 @@ import "core-js/stable";
 import "regenerator-runtime/runtime";
 ```
 
+## Dynamic/Lazy Chunk Loading
+
+For this section, you need Webpack and Webpacker 4. Then enable `SplitChunks` as it is explained in [docs/webpack](docs/webpack.md).
+
+[Dynamic code splitting](https://webpack.js.org/guides/code-splitting#dynamic-imports) enables you to conditionally request/run only the JS that you need. For example, if your site has a `searchBarComponent` on every page, you can reduce the page overhead by deferring the request for the `searchBarComponent` code until after the page has loaded, until the user has scrolled it into view, or until the user has clicked on an element.
+
+```js
+ function loadSearchBarComponent() {
+   return import(/* webpackChunkName: "searchBarComponent" */ './pathTo/searchBarComponent')
+ }
+```
+
+The comment you see above (`/* webpackChunkName */`) is not arbitrary, it is one of webpacks [magic comments](https://webpack.js.org/api/module-methods/#magic-comments). They can be used to fine-tune `import()` with settings such as `defer` or `prefetch`.
+
+**Warning**: You should not attempt to dynamically load anything from your `packs/` folder. Instead, try to make your `pack` scripts a hub from which you dynamically load `non-pack` scripts.
+
+- [Docs for using magic comments](https://webpack.js.org/api/module-methods/#magic-comments)
+- [Docs for configuring `splitChunks` in webpacker](https://github.com/rails/webpacker/blob/master/docs/webpack.md#add-splitchunks-webpack-v4).
+- [Docs for using dynamic `import()`](https://webpack.js.org/guides/code-splitting#dynamic-imports).
 
 ## Module import vs require()