@github/text-expander-element/README.md

Activates a suggestion menu to expand text snippets as you type.

# <text-expander> element

Activates a suggestion menu to expand text snippets as you type.

## Installation

```
$ npm install --save @github/text-expander-element
```

## Usage

### Script

Import as ES modules:

```js
import '@github/text-expander-element'
```

With a script tag:

```html
<script type="module" src="./node_modules/@github/text-expander-element/dist/bundle.js">
```

### Markup

```html
<text-expander keys=": @ #" multiword="#">
  <textarea></textarea>
</text-expander>
```

## Attributes

- `keys` is a space separated list of menu activation keys
- `multiword` defines whether the expansion should use several words or not
  - you can provide a space separated list of activation keys that should support multi-word matching
- `suffix` is a string that is appended to the value during expansion, default is a single space character

## Events

**`text-expander-change`** is fired when a key is matched. In `event.detail` you can find:

- `key`: The matched key; for example: `:`.
- `text`: The matched text; for example: `cat`, for `:cat`.
  - If the `key` is specified in the `multiword` attribute then the matched text can contain multiple words; for example `cat and dog` for `:cat and dog`.
- `provide`: A function to be called when you have the menu results. Takes a `Promise` with `{matched: boolean, fragment: HTMLElement}` where `matched` tells the element whether a suggestion is available, and `fragment` is the menu content to be displayed on the page.

```js
const expander = document.querySelector('text-expander')

expander.addEventListener('text-expander-change', function(event) {
  const {key, provide, text} = event.detail
  if (key !== ':') return

  const suggestions = document.querySelector('.emoji-suggestions').cloneNode(true)
  suggestions.hidden = false
  for (const suggestion of suggestions.children) {
    if (!suggestion.textContent.match(text)) {
      suggestion.remove()
    }
  }
  provide(Promise.resolve({matched: suggestions.childElementCount > 0, fragment: suggestions}))
})
```

The returned fragment should be consisted of filtered `[role=option]` items to be selected. For example:

```html
<ul class="emoji-suggestions" hidden>
  <li role="option" data-value="🐈">🐈 :cat2:</li>
  <li role="option" data-value="🐕">🐕 :dog:</li>
</ul>
```

**`text-expander-value`** is fired when an item is selected. In `event.detail` you can find:

- `key`: The matched key; for example: `:`.
- `item`: The selected item. This would be one of the `[role=option]`. Use this to work out the `value`.
- `value`: A null value placeholder to replace the query. To replace the text query, simply re-assign this value.
- `continue`: A boolean value to specify whether to continue autocompletion after inserting a value. Defaults to `false`. If set to `true`, will not add a space after inserted value and will keep firing the `text-expander-change` event.

```js
const expander = document.querySelector('text-expander')

expander.addEventListener('text-expander-value', function(event) {
  const {key, item}  = event.detail
  if (key === ':') {
    event.detail.value = item.getAttribute('data-value')
  }
})
```

**`text-expander-committed`** is fired after the underlying `input` value has been updated in the DOM. In `event.detail` you can find:

- `input`: The `HTMLInputElement` or `HTMLTextAreaElement` that just had `value` changes committed to the DOM.

```js
const expander = document.querySelector('text-expander')

expander.addEventListener('text-expander-committed', function(event) {
  const {input}  = event.detail
})
```

**`text-expander-activate`** is fired just after the menu has been assigned and appended to the DOM, and just before it is about to be positioned near the text to expand. This is useful for assigning classes or calling imperative methods to show the menu, such as `.showPopover()`.

**`text-expander-deactivate`** is fired just before the menu is going to be unassigned and removed from the DOM. This is useful for removing classes or running cleanup like removing from caches.

## Browser support

Browsers without native [custom element support][support] require a [polyfill][].

- Chrome
- Firefox
- Safari
- Microsoft Edge

[support]: https://caniuse.com/#feat=custom-elementsv1
[polyfill]: https://github.com/webcomponents/custom-elements

## Development

```
npm install
npm test
```

## License

Distributed under the MIT license. See LICENSE for details.