# Finding Components by ID

Retrieve a component by its ID in JavaScript code.

Use `aura:id` to add a local ID of `button1` to the `lightning:button` component.

```nolang
<lightning:button aura:id="button1" label="button1"/>

```

You can find the component by calling `cmp.find("button1")`, where `cmp` is a reference to the component containing the button. The `find()` function has one parameter, which is the local ID of a component within the markup.

`find()` returns different types depending on the result.

- If the local ID is unique, `find()` returns the component.
- If there are multiple components with the same local ID, `find()` returns an array of the components.
- If there is no matching local ID, `find()` returns `undefined`.

**See Also**

- [Component IDs](/docs/platform/aura-platform/guide/components-ids.md)
- [Value Providers](/docs/platform/aura-platform/guide/expr-source.md)