@rsbuild/plugin-node-polyfill

An Rsbuild plugin to automatically inject polyfills for Node.js builtin modules into the browser side.

When to use

Normally, we don't need to use Node builtin modules on the browser side. However, it is possible to use some Node builtin modules when the code will run on both the Node side and the browser side, and this plugin provides browser versions of polyfills for these Node builtin modules.

By using the Node Polyfill plugin, polyfills for Node builtin modules are automatically injected into the browser-side, allowing you to use these modules on the browser side with confidence.

Usage

Install:

npm add @rsbuild/plugin-node-polyfill -D

Add plugin to your rsbuild.config.ts:

// rsbuild.config.ts
import { pluginNodePolyfill } from '@rsbuild/plugin-node-polyfill'

export default {
  plugins: [pluginNodePolyfill()],
}

Node Polyfills

Globals

Buffer
process

When you use the above global variables in your code, the corresponding polyfill will be automatically injected.

For instance, the following code would inject the Buffer polyfill:

const bufferData = Buffer.from('abc')

You can disable this behavior through the globals option of the plugin:

pluginNodePolyfill({
  globals: {
    Buffer: false,
    process: false,
  },
})

Modules

assert
buffer
console
constants
crypto
domain
events
http
https
os
path
punycode
process
querystring
stream
_stream_duplex
_stream_passthrough
_stream_readable
_stream_transform
_stream_writable
string_decoder
sys
timers
tty
url
util
vm
zlib

When the above module is referenced in code via import / require syntax, the corresponding polyfill will be injected.

import { Buffer } from 'buffer'

const bufferData = Buffer.from('abc')

Fallbacks

child_process
cluster
dgram
dns
fs
module
net
readline
repl
tls

Currently there is no polyfill for the above modules on the browser side, so when you import the above modules, it will automatically fallback to an empty object.

import fs from 'fs'

console.log(fs) // -> {}

Options

globals

Used to specify whether to inject polyfills for global variables.

Type:

type Globals = {
  process?: boolean
  Buffer?: boolean
}

Default:

const defaultGlobals = {
  Buffer: true,
  process: true,
}

protocolImports

Whether to polyfill Node.js builtin modules starting with node:.

Type: boolean
Default: true

For example, if you disable protocolImports, modules such as node:path, node:http, etc. will not be polyfilled.

pluginNodePolyfill({
  protocolImports: false,
})

include

Specify an array of modules for which polyfills should be injected. If this option is set, only the specified modules will be polyfilled. include is mutually exclusive with exclude.

Type: string[]
Default: undefined

pluginNodePolyfill({
  include: ['buffer', 'crypto'], // Only "buffer" and "crypto" modules will be polyfilled.
})

exclude

Specify an array of modules for which polyfills should not be injected from the default. If this option is set, the specified modules will be excluded from polyfilled. exclude is mutually exclusive with include.

Type: string[]
Default: undefined

pluginNodePolyfill({
  exclude: ['http', 'https'], // All modules except "http" and "https" will be polyfilled.
})

overrides

Override the default polyfills for specific modules.

Type: Record<string, string>
Default: {}

pluginNodePolyfill({
  overrides: {
    fs: 'memfs',
  },
})

Exported variables

builtinMappingResolved: A map of Node.js builtin modules to their resolved corresponding polyfills modules.
resolvedPolyfillToModules: A map of resolved polyfill modules to the polyfill modules before resolving.

License

MIT.