[Home](./index.md) > [@firebase/firestore](./firestore.md) > [/](./firestore_.md) > [LoadBundleTask](./firestore_.loadbundletask.md) > [then](./firestore_.loadbundletask.then.md) ## LoadBundleTask.then() method Implements the `Promise.then` interface. Signature: ```typescript then(onFulfilled?: (a: LoadBundleTaskProgress) => T | PromiseLike, onRejected?: (a: Error) => R | PromiseLike): Promise; ``` ## Parameters | Parameter | Type | Description | | --- | --- | --- | | onFulfilled | (a: [LoadBundleTaskProgress](./firestore_.loadbundletaskprogress.md)) => T \| PromiseLike<T> | Called on the completion of the loading task with a final LoadBundleTaskProgress update. The update will always have its taskState set to "Success". | | onRejected | (a: Error) => R \| PromiseLike<R> | Called when an error occurs during bundle loading. | Returns: Promise<T \| R>