Bundler API

Rolldown provides three main API functions for bundling your code programmatically.

rolldown()

rolldown() is the API compatible with Rollup's rollup function.

import { rolldown } from 'rolldown';

let bundle,
  failed = false;
try {
  bundle = await rolldown({
    input: 'src/main.js',
  });
  await bundle.write({
    format: 'esm',
  });
} catch (e) {
  console.error(e);
  failed = true;
}
if (bundle) {
  await bundle.close();
}
process.exitCode = failed ? 1 : 0;

See its reference for more details.

watch()

watch() is the API compatible with Rollup's watch function.

import { watch } from 'rolldown';

const watcher = watch({
  /* ... */
});
watcher.on('event', (event) => {
  if (event.code === 'BUNDLE_END') {
    console.log(event.duration);
    event.result.close();
  }
});

// Stop watching
watcher.close();

See its reference for more details.

build()

Experimental

This API is experimental and may change in patch releases.

build() is the simplest option for most use cases. The API is similar to esbuild's build function. It bundles and writes in a single call with automatic cleanup.

import { build } from 'rolldown';

const result = await build({
  input: 'src/main.js',
  output: {
    file: 'bundle.js',
  },
});
console.log(result);

See its reference for more details.