# Source: https://rspack.dev/plugins/rspack/swc-js-minimizer-rspack-plugin.md

# SwcJsMinimizerRspackPlugin

Rspack only
This plugin is used to minify JavaScript files using [SWC](https://swc.rs/).

## Example

Use this plugin via [optimization.minimizer](/config/optimization.md#optimizationminimizer):

```js title="rspack.config.mjs"
import { rspack } from '@rspack/core';

export default {
  optimization: {
    minimizer: [
      new rspack.SwcJsMinimizerRspackPlugin({
        // options
      }),
      new rspack.LightningCssMinimizerRspackPlugin(),
    ],
  },
};
```

:::tip
When `optimization.minimizer` is set, the default minimizers are disabled, so we need to add [LightningCssMinimizerRspackPlugin](/plugins/rspack/lightning-css-minimizer-rspack-plugin.md) to minify CSS files.
:::

## Options

### test

- **Type:** `string | RegExp | Array<string | RegExp>`
- **Default:** `\.[cm]?js(\?.*)?$`

Specify the files to be minimized. You can use regular expressions or file path strings, and only the files that match will be minimized.

For example, the build generates `/dist/foo.[hash].js` and some other JS files, we only minify `foo.js`:

```js
new rspack.SwcJsMinimizerRspackPlugin({
  test: /dist\/foo\.\w+\.js$/,
});
```

### include

- **Type:** `string | RegExp | Array<string | RegExp>`
- **Default:** `undefined`

Same as `test`, specify the files to be minimized.

```js
new rspack.SwcJsMinimizerRspackPlugin({
  include: /dist\/foo\.\w+\.js$/,
});
```

### exclude

- **Type:** `string | RegExp | Array<string | RegExp>`
- **Default:** `undefined`

Specify the files to be excluded. You can use regular expressions or file path strings, and the files that match will not be minimized.

For example, the build generates `/dist/foo.[hash].js` and some other JS files, we exclude the minimization of `foo.js`:

```js
new rspack.SwcJsMinimizerRspackPlugin({
  exclude: /dist\/foo\.\w+\.js$/,
});
```

### extractComments

- **Type:**

```ts
type ExtractCommentsOptions =
  | boolean
  | RegExp
  | {
      condition?: boolean | RegExp | undefined;
      banner?: string | boolean | undefined;
    };
```

- **Default:** `undefined`

Whether comments shall be extracted to a separate file. If the original file is named `foo.js`, then the comments will be stored to `foo.js.LICENSE.txt`.

#### boolean

If value is `true`, it is equivalent to `/@preserve|@lic|@cc_on|^\**!/` regexp condition and remove remaining comments.

```js
new rspack.SwcJsMinimizerRspackPlugin({
  extractComments: {
    condition: /@preserve|@lic|@cc_on|^\**!/,
  },
});
```

If value is `false`, all comments will be removed.

```js
new rspack.SwcJsMinimizerRspackPlugin({
  extractComments: false,
});
```

#### RegExp

If value is `RegExp`, all comments that match the given expression will be extracted to the separate file.

```js
new rspack.SwcJsMinimizerRspackPlugin({
  extractComments: /@preserve|@lic|@cc_on|^\**!/,
});
```

#### object

If value is `object`, it can use `condition` and `banner` to customize the extraction.

```js
new rspack.SwcJsMinimizerRspackPlugin({
  extractComments: {
    // add comments that match the condition will be extracted
    condition: /@preserve|@lic|@cc_on|^\**!/,
    // add banner to the top of the `*.LICENSE.txt` file
    // If `true`, use the default banner `/*! For license information please see {relative} */`
    // If `false`, no banner will be added
    // If `string`, use the given banner
    banner: true,
  },
});
```

### minimizerOptions

- **Type:**

```ts
type MinimizerOptions = {
  minify?: boolean;
  module?: boolean;
  ecma?: 5 | 2015 | 2016 | string | number;
  mangle?: TerserMangleOptions | boolean;
  compress?: TerserCompressOptions | boolean;
  format?: JsFormatOptions & ToSnakeCaseProperties<JsFormatOptions>;
};
```

- **Default:**

```js
const defaultOptions = {
  minify: true,
  mangle: true,
  ecma: 5, // or derived from Rspack's target configuration
  compress: {
    passes: 2,
  }
  format: {
    comments: false,
  },
};
```

:::tip Default ecma from Rspack target
If `ecma` is not specified, `SwcJsMinimizerRspackPlugin` will automatically derive a default value from Rspack's [`target`](/config/target.md) configuration. Otherwise, it defaults to `5`.

This means you can rely on your Rspack `target` configuration without manually specifying the same ecma version in the plugin options.
:::

Similar to the `jsc.minify` option of SWC, please refer to [SWC - Minification](https://swc.rs/docs/configuration/minification) for all available options.

For example, disable `mangle` to avoid mangling variable names:

```js
new rspack.SwcJsMinimizerRspackPlugin({
  minimizerOptions: {
    mangle: false,
  },
});
```

For example, set a higher `passes` to run more compression passes. In some cases this may result in a smaller bundle size, but the more passes that are run, the more time it takes to compress.

```js
new rspack.SwcJsMinimizerRspackPlugin({
  minimizerOptions: {
    compress: {
      passes: 4,
    },
  },
});
```