JavaScript Building

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.

Options

targetPath [string]

If not set, the source path will be used as the base target path. Note that the target path’s extension may change if the target MIME type is different, e.g. when the source is TypeScript.

params [map or slice]

Params that can be imported as JSON in your JS files, e.g.:

{{ $js := resources.Get "js/main.js" | js.Build (dict "params" (dict "api" "https://example.org/api")) }}

And then in your JS file:

import * as params from '@params';

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.

minify [bool]

Let js.Build handle the minification.

inject [slice]

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

shims

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:

{{ $shims := dict "react" "js/shims/react.js"  "react-dom" "js/shims/react-dom.js" }}
{{ $js = $js | js.Build dict "shims" $shims }}

The shim files may look like these:

// js/shims/react.js
module.exports = window.React;

// js/shims/react-dom.js
module.exports = window.ReactDOM;

With the above, these imports should work in both scenarios:

import * as React from 'react'
import * as ReactDOM from 'react-dom';

target [string]

The language target. One of: es5, es2015, es2016, es2017, es2018, es2019, es2020 or esnext. Default is esnext.

externals [slice]

External dependencies. Use this to trim dependencies you know will never be executed. See https://esbuild.github.io/api/#external

defines [map]

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.

{{ $defines := dict "process.env.NODE_ENV" `"development"` }}

format [string]

The output format. One of: iife, cjs, esm. Default is iife, a self-executing function, suitable for inclusion as a tag.

sourceMap

Whether to generate inline or external sourcemap from esbuild. External sourcemaps will be written to the target with the output filename + “.map”. Input sourcemaps can be read from js.Build and node modules and combined into the output sourcemaps.

Import JS code from /assets

js.Build has full support for the virtual union file system in Hugo Modules. You can see some simple examples in this test project, but in short this means that you can do this:

import { hello } from 'my/module';

And it will resolve to the top-most index.{js,ts,tsx,jsx} inside assets/my/module in the layered file system.

import { hello3 } from 'my/module/hello3';

Will resolve to hello3.{js,ts,tsx,jsx} inside assets/my/module.

Any imports starting with . is resolved relative to the current file:

import { hello4 } from './lib';

For other files (e.g. JSON, CSS) you need to use the relative path including any extension, e.g:

import * as data from 'my/module/data.json';

Any imports in a file outside /assets or that does not resolve to a component inside /assets will be resolved by ESBuild 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. If you have any imported npm dependencies in your project, you need to make sure to run npm install before you run hugo.

Also note the new params option that can be passed from template to your JS files, e.g.:

{{ $js := resources.Get "js/main.js" | js.Build (dict "params" (dict "api" "https://example.org/api")) }}

And then in your JS file:

import * as params from '@params';

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.

Include Dependencies In package.json / node_modules

Any imports in a file outside /assets or that does not resolve to a component inside /assets will be resolved by ESBuild 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. If you have any imported npm dependencies in your project, you need to make sure to run npm install before you run hugo.

The start directory for resolving npm packages (aka. packages that live inside a node_modules folder) is always the main project folder.

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, a tool to consolidate all the npm dependencies in a project.

Examples

{{ $built := resources.Get "js/index.js" | js.Build "main.js" }}

Or with options:

{{ $externals := slice "react" "react-dom" }}
{{ $defines := dict "process.env.NODE_ENV" `"development"` }}

{{ $opts := dict "targetPath" "main.js" "externals" $externals "defines" $defines }}
{{ $built := resources.Get "scripts/main.js" | js.Build $opts }}
<script src="{{ $built.RelPermalink }}" defer></script>