js.md (6432B)
1 ---
2 title: JavaScript Building
3 description: Hugo Pipes can process JavaScript files with [ESBuild](https://github.com/evanw/esbuild).
4 date: 2020-07-20
5 publishdate: 2020-07-20
6 lastmod: 2020-07-20
7 categories: [asset management]
8 keywords: []
9 menu:
10 docs:
11 parent: "pipes"
12 weight: 45
13 weight: 45
14 sections_weight: 45
15 draft: false
16 ---
17
18 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.
19
20 ### Options
21
22 targetPath [string]
23 : If not set, the source path will be used as the base target path.
24 Note that the target path's extension may change if the target MIME type is different, e.g. when the source is TypeScript.
25
26 params [map or slice] {{< new-in "0.78.0" >}}
27 : Params that can be imported as JSON in your JS files, e.g.:
28
29 ```go-html-template
30 {{ $js := resources.Get "js/main.js" | js.Build (dict "params" (dict "api" "https://example.org/api")) }}
31 ```
32 And then in your JS file:
33
34 ```js
35 import * as params from '@params';
36 ```
37
38 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.
39
40 minify [bool]
41 : Let `js.Build` handle the minification.
42
43 inject [slice] {{< new-in "0.81.0" >}}
44 : This option allows you to automatically replace a global variable with an import from another file. The path names must be relative to `assets`. See https://esbuild.github.io/api/#inject
45
46 shims {{< new-in "0.81.0" >}}
47 : This option allows swapping out a component with another. A common use case is to load dependencies like React from a CDN (with _shims_) when in production, but running with the full bundled `node_modules` dependency during development:
48
49 ```
50 {{ $shims := dict "react" "js/shims/react.js" "react-dom" "js/shims/react-dom.js" }}
51 {{ $js = $js | js.Build dict "shims" $shims }}
52 ```
53
54 The _shim_ files may look like these:
55
56 ```js
57 // js/shims/react.js
58 module.exports = window.React;
59 ```
60
61 ```js
62 // js/shims/react-dom.js
63 module.exports = window.ReactDOM;
64 ```
65
66
67 With the above, these imports should work in both scenarios:
68
69 ```js
70 import * as React from 'react'
71 import * as ReactDOM from 'react-dom';
72 ```
73
74 target [string]
75 : The language target.
76 One of: `es5`, `es2015`, `es2016`, `es2017`, `es2018`, `es2019`, `es2020` or `esnext`.
77 Default is `esnext`.
78
79 externals [slice]
80 : External dependencies. Use this to trim dependencies you know will never be executed. See https://esbuild.github.io/api/#external
81
82
83 defines [map]
84 : 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.
85
86 ```go-html-template
87 {{ $defines := dict "process.env.NODE_ENV" `"development"` }}
88 ```
89
90 format [string] {{< new-in "0.74.3" >}}
91 : The output format.
92 One of: `iife`, `cjs`, `esm`.
93 Default is `iife`, a self-executing function, suitable for inclusion as a <script> tag.
94
95 sourceMap
96 : Whether to generate source maps. Enum, currently only `inline` (we will improve that).
97
98 ### Import JS code from /assets
99
100 {{< new-in "0.78.0" >}}
101
102 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:
103
104 ```js
105 import { hello } from 'my/module';
106 ```
107
108 And it will resolve to the top-most `index.{js,ts,tsx,jsx}` inside `assets/my/module` in the layered file system.
109
110 ```js
111 import { hello3 } from 'my/module/hello3';
112 ```
113
114 Will resolve to `hello3.{js,ts,tsx,jsx}` inside `assets/my/module`.
115
116 Any imports starting with `.` is resolved relative to the current file:
117
118 ```js
119 import { hello4 } from './lib';
120 ```
121
122 For other files (e.g. `JSON`, `CSS`) you need to use the relative path including any extension, e.g:
123
124 ```js
125 import * as data from 'my/module/data.json';
126 ```
127
128 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`.
129
130 Also note the new `params` option that can be passed from template to your JS files, e.g.:
131
132 ```go-html-template
133 {{ $js := resources.Get "js/main.js" | js.Build (dict "params" (dict "api" "https://example.org/api")) }}
134 ```
135 And then in your JS file:
136
137 ```js
138 import * as params from '@params';
139 ```
140
141 Hugo will, by default, generate a `assets/jsconfig.json` 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).
142
143
144
145 ### Include Dependencies In package.json / node_modules
146
147 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`.
148
149 {{< 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.
150
151 **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.
152
153
154 ### Examples
155
156 ```go-html-template
157 {{ $built := resources.Get "js/index.js" | js.Build "main.js" }}
158 ```
159
160 Or with options:
161
162 ```go-html-template
163 {{ $externals := slice "react" "react-dom" }}
164 {{ $defines := dict "process.env.NODE_ENV" `"development"` }}
165
166 {{ $opts := dict "targetPath" "main.js" "externals" $externals "defines" $defines }}
167 {{ $built := resources.Get "scripts/main.js" | js.Build $opts }}
168 <script type="text/javascript" src="{{ $built.RelPermalink }}" defer></script>
169 ```
170
171