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# Calypso Async Babel Transform Plugin
`babel-plugin-transform-wpcalypso-async` is a Babel plugin to facilitate optional
code-splitting by applying transformations to a `asyncRequire` global function or the
[`<AsyncLoad />` React component](https://github.com/Automattic/wp-calypso/tree/HEAD/client/components/async-load).
## Usage
Include in your Babel configuration as a plugin.
Example Babel config file:
```json
{
"plugins": [ "@automattic/transform-wpcalypso-async" ]
}
```
See [Babel options documentation](http://babeljs.io/docs/usage/options/) for more information.
## Transformations
`asyncRequire` will transform to one of:
- dynamic `import()` if the `ignore` plugin option is not `true`
- a rejected `Promise` that throws an error that the import is ignored, if the `ignore` plugin option is `true`
`asyncRequire` expects one required argument, the name of the imported module.
```js
asyncRequire( 'calypso/components/search' ).then( ( { default: Search } ) => {
console.log( Search );
} );
```
`<AsyncLoad />` will transform its `require` string prop to a function invoking a dynamic `import`, or throwing an error when the `ignore` option is enabled.
```js
// Before:
<AsyncLoad require="calypso/components/search" />;
```
```js
// After:
const ref = () => import( 'calypso/components/search' );
<AsyncLoad require={ ref } />;
```
## Options
- `ignore` - if set to `true`, the `asyncRequire` call will be returning a rejected `Promise`, and `AsyncLoad` will show the placeholder forever and won't do any import. Useful for server side rendering where the render is one-pass and doesn't wait for any imports to finish.
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