Macros are a mechanism for running JavaScript functions at bundle-time. The value returned from these functions or variables are directly inlined into your bundle.

# npm
npm i -D unplugin-macros

# jsr
npx jsr add -D @unplugin/macros

// vite.config.ts
import Macros from 'unplugin-macros/vite'

export default defineConfig({
  plugins: [Macros()],
})

// rollup.config.js
import Macros from 'unplugin-macros/rollup'

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

// esbuild.config.js
import { build } from 'esbuild'

build({
  plugins: [require('unplugin-macros/esbuild')()],
})

// webpack.config.js
module.exports = {
  /* ... */
  plugins: [require('unplugin-macros/webpack')()],
}

// main.js
import { buildTime, getRandom } from './macros' with { type: 'macro' }

getRandom() // Will be replaced with a random number at build time
buildTime // Will be replaced with the timestamp at the build time

// macros.js
export function getRandom() {
  return Math.random()
}
export const buildTime = Date.now()

You can pass function values as arguments to macros. Functions must be isolated (no references to outside identifiers):

// main.js
import { transform } from './macros' with { type: 'macro' }

transform(() => 42)
transform(async () => await Promise.resolve(42))

See more in Bun Macros.

Import Attributes syntax is supported in TypeScript 5.3 and above.

Import Attributes syntax is supported in ESLint v9.14.0.

Refer to docs.

Thanks to Bun Macros.

MIT License © 2023-PRESENT Kevin Deng