wp-calypso/packages/components/src/select-dropdown/README.md

# Select Dropdown

React component used to display a dropdown selector.

It can be utilized via two different techniques: children components or an options array. These techniques are available because certain use cases prefer the "selection" logic to be built into `SelectDropdown`, while others prefer to explicitly define that logic elsewhere.

---

## Using Children

The children technique is appropriate when you'd like to define the "selection" logic at the same point where `<SelectDropdown>` is implemented.

A good example for this case is navigation. Sometimes the option that is selected is defined by the route, other times it's a state value, external prop, etc.

```jsx
import SelectDropdown from 'calypso/components/select-dropdown';

export default function MyComponent() {
	return (
		<SelectDropdown selectedText="Published">
			<SelectDropdown.Item selected path="/published">
				Published
			</SelectDropdown.Item>
			<SelectDropdown.Item path="/scheduled">Scheduled</SelectDropdown.Item>
			<SelectDropdown.Item path="/drafts">Drafts</SelectDropdown.Item>
			<SelectDropdown.Item path="/trashed">Trashed</SelectDropdown.Item>
		</SelectDropdown>
	);
}
```

The key here is that it's up to the parent component to explicitly define things like: which item is selected, what the selected text is (used in the dropdown header), and potentially `onClick` callbacks, etc.

### Props

#### Select Dropdown

`selectedText`

Used for displaying the text on the dropdown header.

![selectedText example screenshot](https://cldup.com/Da_dTXN4mF.png)

`selectedCount`

Used for displaying the count on the dropdown header.

`selectedIcon`

Used for displaying an icon on the dropdown header.

`className`

Optional extra class(es) to be applied to the `.select-dropdown`.

`tabIndex`

Optional tabIndex setting to override tab order via keyboard navigation. By default this is set to `0` which simply puts the element in the tabbing flow according to the component's placement in the document.

`disabled`

Used to determine whether the select dropdown is in a disabled state. When disabled it will not respond to interaction and will render to appear disabled.

`ariaLabel`

Optional dropdown header label that can be used to improve the accessibility for screen readers.

#### Dropdown Item

`selected`

Boolean representing the selected visual state. `selected={ true }` creates a blue background on the selected item.

`count`

Optional number to show a Count next to the item text.

![selected example screenshot](https://cldup.com/BOZktaoqTT.png)

`icon`

Optional icon to show before the item text.

`path`

Optional URL to navigate to when option is clicked.

`disabled`

Optional bool to disable dropdown item.

`onClick`

Optional callback that will be applied when a `SelectDropdown.Item` has been clicked. This could be used for updating a parent's state, tracking analytics, etc.

`ariaLabel`

Optional dropdown item label that can be used to improve the accessibility for screen readers.

### Label

An item "label" can be added like as a sibling to `SelectDropdown.Item`. The purpose
of this `SelectDropdown.Label` component is used to display a static item, for example, to group
items.

### Separator

As a sibling to `SelectDropdown.Item`, an item "separator" or horizontal line can be used to visually separate items.

![separator example screenshot](https://cldup.com/CWEH2K9PUf.png)

```js
import SelectDropdown from 'calypso/components/select-dropdown';

export default class extends React.Component {
	// ...

	render() {
		return (
			<SelectDropdown selectedText="Published">
				<SelectDropdown.Label>
					<em>Post status</em>
				</SelectDropdown.Label>
				<SelectDropdown.Item selected path="/published">
					Published
				</SelectDropdown.Item>
				<SelectDropdown.Item path="/scheduled">Scheduled</SelectDropdown.Item>
				<SelectDropdown.Item path="/drafts">Drafts</SelectDropdown.Item>
				<SelectDropdown.Separator />
				<SelectDropdown.Item path="/trashed">Trashed</SelectDropdown.Item>
			</SelectDropdown>
		);
	}
}
```

---

## Using options array

`SelectDropdown` can also be used by passing in an `options` array as a prop. This technique is great for situations where you don't want to explicitly define things like what happens when an item is clicked or which item is currently selected, etc.

A good example for this case is a form element. You don't want to have to write the logic for updating the component when a new selection is made, but you might want to hook into certain events like: when a new selection is made, what was the option?

> **NOTE** - there is still more work here in order to be fully functional as a form element, not recommended use case... yet.

```js
import SelectDropdown from 'calypso/components/select-dropdown';

const options = [
	{ label: 'Post status', isLabel: true },
	{ value: 'published', label: 'Published' },
	{ value: 'scheduled', label: 'Scheduled' },
	{ value: 'drafts', label: 'Drafts' },
	{ value: 'trashed', label: 'Trashed' },
];

export default class extends React.Component {
	// ...

	handleOnSelect = ( option ) => {
		console.log( 'selected option:', option ); // full object of selected option
	};

	render() {
		return <SelectDropdown options={ options } onSelect={ this.handleOnSelect } />;
	}
}
```

Note that all the "selection" logic will be applied in `SelectDropdown` itself using a simple `selected` value comparison in state. It will update itself when an option has been clicked.

### Props

`options`

The main data set for rendering out the various options.

```js
const options = [
	{
		value: 'the value', // *required* - (string) tracked by component
		label: 'the label', // *required* - (string) displayed to user
		isLabel: true, // optional - (boolean) set this item like a static label
		path: '/', // optional - (string) URL to navigate when clicked
	},
	// ...
];
```

`initialSelected`

Optional string representing the initial selected option's `value`. Default will be the first option's `value`.

`compact`

Optional boolean indicating the dropdown will be rendered in compact mode

`onSelect`

Optional callback that will be run whenever a new selection has been clicked.

`onToggle`

Optional callback that will be run after the dropdown is opened or closed. An event object is passed, including a `target` property equal to the `SelectDropdown` React element instance, and `open` equal to the current toggle state of the dropdown.

### Label

Adding `isLabel` key set to `true` into the item object will create a `SelectDropdown.Label` component.

```js
const options = [
	{ label: 'Post status', isLabel: true },
	{ value: 'published', label: 'Published' },
	{ value: 'scheduled', label: 'Scheduled' },
	{ value: 'drafts', label: 'Drafts' },
	null,
	{ value: 'trashed', label: 'Trashed' },
];
```

### Separator

Using a `null` or `false` item in the `options` will render an item "separator" or horizontal line can be used to visually separate items.

![separator example screenshot](https://cldup.com/CWEH2K9PUf.png)

```js
const options = [
	{ value: 'published', label: 'Published' },
	{ value: 'scheduled', label: 'Scheduled' },
	{ value: 'drafts', label: 'Drafts' },
	null,
	{ value: 'trashed', label: 'Trashed' },
];
```