# rollup-plugin-banner2

## Introduction

Rollup plugin to prepend content before bundled js code.

## Why

`rollup` itself contains `output.banner` option.
The difference between this plugin and the `output.banner` parameter provided by the rollup is that the banner will not be cleaned up - for example by `rollup-plugin-uglify` plugin, the output file will not contain the `output.banner` parameter you set. `rollup-plugin-banner2` solves this problem.

There is another banner plugin: https://github.com/yingye/rollup-plugin-banner . Unfortunately, it looks **NOT MAINTAINED** for quite some time now. The main differences are described below.

## Usage

Install the plugin with NPM:

```
npm install --save-dev rollup-plugin-banner2
```

Add it to your rollup configuration:

```js
import banner2 from 'rollup-plugin-banner2'

export default {
  plugins: [
    banner2(() => `
    /**
     * rollup-plugin-banner2
     */
    `)
  ]
}

```

## Comparison with `rollup-plugin-banner`
- `banner2` supports sourcemaps
- `banner2` supports adding different banner to different chunks based on `ChunkInfo` (for more info see https://rollupjs.org/ )
- `banner2` does not support file path option that loads a file content and uses that as a banner. It should be easy enough to call `fs.readFileSync` yourself
- `banner2` does not support injecting values from `package.json` to banner via `<%= pkg.author %>` etc.
- `banner2` does not add JS comments as a wrapper to every banner

The missing features could be added if someone actually needs them.

## API

```ts
banner2(resolveBanner, options)
```
The `resolveBanner` function returns a banner as `string`,
or possibly a `Promise` resolving a `string`

For more details see the [typescript definition](index.d.ts)