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PouchDB has an asynchronous API, supporting both [callbacks](http://docs.nodejitsu.com/articles/getting-started/control-flow/what-are-callbacks) and [promises][promise].

Most of the API is exposed as:

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db.doSomething(args..., [options], [callback])
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&hellip; where both the `options` and `callback` are optional.

Callbacks use the standard Node.js idiom of:

{% highlight js %}
function(error, result) { /* ... */ }
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&hellip; where the `error` will be undefined if there's no error.

If you don't specify a `callback`, then the API returns a [promise][]. In [supported browsers](http://caniuse.com/#feat=promises), native promises are used, falling back to the minimal library [lie][] as needed. In Node.js, promises come from [Bluebird][].

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**Using Ionic/Angular?**  You can wrap PouchDB promises in [`$q.when()`](https://docs.angularjs.org/api/ng/service/$q#when). This will notify Angular to update the UI when the PouchDB promise has resolved.

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For more info, check out the [guide to asynchronous code](/guides/async-code.html).

[promise]: https://www.promisejs.org/
[lie]: https://github.com/calvinmetcalf/lie
[bluebird]: https://github.com/petkaantonov/bluebird
[event emitter]: http://nodejs.org/api/events.html#events_class_events_eventemitter