174 lines
7.4 KiB
Markdown
174 lines
7.4 KiB
Markdown
---
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title: JavaScript Building
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description: Hugo Pipes can process JavaScript files with [ESBuild](https://github.com/evanw/esbuild).
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date: 2020-07-20
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publishdate: 2020-07-20
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lastmod: 2020-07-20
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categories: [asset management]
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keywords: []
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menu:
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docs:
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parent: "pipes"
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weight: 45
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weight: 45
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sections_weight: 45
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draft: false
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---
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Any JavaScript resource file can be transpiled and "tree shaken" using `js.Build` which takes for argument either a string for the filepath or a dict of options listed below.
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### Options
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targetPath [string]
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: If not set, the source path will be used as the base target path.
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Note that the target path's extension may change if the target MIME type is different, e.g. when the source is TypeScript.
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params [map or slice] {{< new-in "0.78.0" >}}
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: Params that can be imported as JSON in your JS files, e.g.:
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```go-html-template
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{{ $js := resources.Get "js/main.js" | js.Build (dict "params" (dict "api" "https://example.org/api")) }}
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```
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And then in your JS file:
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```js
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import * as params from '@params';
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```
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Note that this is meant for small data sets, e.g. config settings. For larger data, please put/mount the files into `/assets` and import them directly.
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minify [bool]
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: Let `js.Build` handle the minification.
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avoidTDZ {{< new-in "0.78.0" >}}
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: There is/was a bug in WebKit with severe performance issue with the tracking of TDZ checks in JavaScriptCore. Enabling this flag removes the TDZ and `const` assignment checks and may improve performance of larger JS codebases until the WebKit fix is in widespread use. See https://bugs.webkit.org/show_bug.cgi?id=199866
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target [string]
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: The language target.
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One of: `es5`, `es2015`, `es2016`, `es2017`, `es2018`, `es2019`, `es2020` or `esnext`.
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Default is `esnext`.
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externals [slice]
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: External dependencies. If a dependency should not be included in the bundle (Ex. library loaded from a CDN.), it should be listed here.
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```go-html-template
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{{ $externals := slice "react" "react-dom" }}
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```
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> Marking a package as external doesn't imply that the library can be loaded from a CDN. It simply tells Hugo not to expand/include the package in the JS file.
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defines [map]
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: Allow to define a set of string replacement to be performed when building. Should be a map where each key is to be replaced by its value.
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```go-html-template
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{{ $defines := dict "process.env.NODE_ENV" `"development"` }}
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```
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format [string] {{< new-in "0.74.3" >}}
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: The output format.
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One of: `iife`, `cjs`, `esm`.
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Default is `iife`, a self-executing function, suitable for inclusion as a <script> tag.
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sourceMap
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: Whether to generate source maps. Enum, currently only `inline` (we will improve that).
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### Import JS code from /assets
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{{< new-in "0.78.0" >}}
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Since Hugo `v0.78.0` `js.Build` has full support for the virtual union file system in [Hugo Modules](/hugo-modules/). You can see some simple examples in this [test project](https://github.com/gohugoio/hugoTestProjectJSModImports), but in short this means that you can do this:
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```js
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import { hello } from 'my/module';
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```
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And it will resolve to the top-most `index.{js,ts,tsx,jsx}` inside `assets/my/module` in the layered file system.
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```js
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import { hello3 } from 'my/module/hello3';
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```
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Wil resolve to `hello3.{js,ts,tsx,jsx}` inside `assets/my/module`.
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Any imports starting with `.` is resolved relative to the current file:
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```js
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import { hello4 } from './lib';
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```
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For other files (e.g. `JSON`, `CSS`) you need to use the relative path including any extension, e.g:
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```js
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import * as data from 'my/module/data.json';
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```
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Any imports in a file outside `/assets` or that does not resolve to a component inside `/assets` will be resolved by [ESBuild](https://esbuild.github.io/) with the **project directory** as the resolve directory (used as the starting point when looking for `node_modules` etc.). Also see [hugo mod npm pack](/commands/hugo_mod_npm_pack/). If you have any imported NPM dependencies in your project, you need to make sure to run `npm install` before you run `hugo`.
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Also note the new `params` option that can be passed from template to your JS files, e.g.:
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```go-html-template
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{{ $js := resources.Get "js/main.js" | js.Build (dict "params" (dict "api" "https://example.org/api")) }}
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```
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And then in your JS file:
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```js
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import * as params from '@params';
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```
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Hugo will, by default, generate a `assets/jsconfig.js` file that maps the imports. This is useful for navigation/intellisense help inside code editors, but if you don't need/want it, you can [turn it off](/getting-started/configuration/#configure-build).
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### Include Dependencies In package.json / node_modules
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Any imports in a file outside `/assets` or that does not resolve to a component inside `/assets` will be resolved by [ESBuild](https://esbuild.github.io/) with the **project directory** as the resolve directory (used as the starting point when looking for `node_modules` etc.). Also see [hugo mod npm pack](/commands/hugo_mod_npm_pack/). If you have any imported NPM dependencies in your project, you need to make sure to run `npm install` before you run `hugo`.
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{{< new-in "0.78.1" >}} From Hugo `0.78.1` the start directory for resolving NPM packages (aka. packages that live inside a `node_modules` folder) is always the main project folder.
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**Note:** If you're developing a theme/component that is supposed to be imported and depends on dependencies inside `package.json`, we recommend reading about [hugo mod npm pack](/commands/hugo_mod_npm_pack/), a tool to consolidate all the NPM dependencies in a project.
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### Examples
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```go-html-template
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{{ $built := resources.Get "js/index.js" | js.Build "main.js" }}
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```
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Or with options:
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```go-html-template
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{{ $externals := slice "react" "react-dom" }}
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{{ $defines := dict "process.env.NODE_ENV" `"development"` }}
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{{ $opts := dict "targetPath" "main.js" "externals" $externals "defines" $defines }}
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{{ $built := resources.Get "scripts/main.js" | js.Build $opts }}
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<script type="text/javascript" src="{{ $built.RelPermalink }}" defer></script>
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```
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#### Shimming a JS library
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It's a very common practice to load external libraries using CDN rather than importing all packages in a single JS file, making it bulky. To do the same with Hugo, you'll need to shim the libraries as follows. In this example, `algoliasearch` and `instantsearch.js` will be shimmed.
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Firstly, add the following to your project's `package.json`:
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```json
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{
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"browser": {
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"algoliasearch/lite": "./public/js/shims/algoliasearch.js",
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"instantsearch.js/es/lib/main": "./public/js/shims/instantsearch.js"
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}
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}
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```
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What this does is it tells Hugo to look for the listed packages somewhere else. Here we're telling Hugo to look for `algoliasearch/lite` and `instantsearch.js/es/lib/main` in the project's `public/js/shims` folder.
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Now we'll need to create the shim JS files which export the global JS variables `module.exports = window.something`. You can create a separate shim JS file in your `assets` directory, and redirect the import paths there if you wish, but a much cleaner way is to create these files on the go, by having the following before your JS is built.
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```go-html-template
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{{ $a := "module.exports = window.algoliasearch" | resources.FromString "js/shims/algoliasearch.js" }}
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{{ $i := "module.exports = window.instantsearch" | resources.FromString "js/shims/instantsearch.js" }}
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{{/* Call RelPermalink unnecessarily to generate JS files */}}
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{{ $placebo := slice $a.RelPermalink $i.RelPermalink }}
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```
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That's it! You should now have a browser-friendly JS which can use external JS libraries.
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