Node.js loader with a Rollup-like interface.
unloader is a Node.js loader framework. Similar to Rollup as a general bundler, unloader provides customization capabilities through a subset of Rollup plugin API.
unloader is designed to be a general-purpose loader, which can be used to develop various loaders, such as Oxc loader, TypeScript loader, etc.
Node.js v22.18 and above
npm i unloadernode --import unloader/register ...| Hook | Description |
|---|---|
options |
Modify the options from userland. |
resolveId |
Resolve the module id. |
load |
Load the module. |
transform |
Transform the module. |
unloader supports both ESM and CJS. All hooks are synchronous.
import { readFileSync } from 'node:fs'
import type { Plugin } from 'unloader'
const plugin: Plugin = {
name: 'my-plugin',
resolveId(source, importer, options) {
const result = this.resolve(`${source}.js`, importer, options)
if (result) {
console.log(result)
return result
}
},
load(id) {
const contents = readFileSync(id, 'utf8')
console.log(contents)
return contents
},
}demo.ts
let context: PluginContext
export function demoPlugin(): Plugin {
return {
name: 'demo-plugin',
options(config) {
config.sourcemap = true
},
buildStart(_context) {
context = _context
context.log('hello world')
},
resolveId(source, importer, options) {
if (source.startsWith('node:')) return
// Feature: virtual module
if (source === 'virtual-mod') {
return '/virtual-mod'
}
// Feature: try resolve with different extensions
const result = this.resolve(`${source}.js`, importer, options)
if (result) return result
},
load(id) {
if (id === '/virtual-mod') {
return { code: 'export const count = 42' }
}
},
transform(code, id) {
if (typeof code === 'string') {
// Feature: source map
const s = new MagicString(code)
s.prepend('// header\n')
const map = s.generateMap({
file: id,
hires: 'boundary',
includeContent: true,
})
return {
code: s.toString(),
map,
}
}
},
}
}See demo plugin and unloader.config.ts for more details.
unloader is supported as a framework in unplugin.
// unloader.config.ts
import Oxc from 'unplugin-oxc/unloader'
export default {
plugins: [
Oxc({
// options
}),
],
}- Thanks to tsx!
MIT License © 2025-PRESENT Kevin Deng