iron-collapse - Vaadin Add-on Directory
Adds collapsible behavior to a target element
[](https://www.npmjs.com/package/@polymer/iron-collapse)
[](https://travis-ci.org/PolymerElements/iron-collapse)
[](https://webcomponents.org/element/@polymer/iron-collapse)
## <iron-collapse>
`iron-collapse` creates a collapsible block of content. By default, the content
will be collapsed. Use `opened` or `toggle()` to show/hide the content. The
aria-expanded attribute should only be set on the button that controls the
collapsable area, not on the area itself. See
https://www.w3.org/WAI/GL/wiki/Using_aria-expanded_to_indicate_the_state_of_a_collapsible_element#Description
`iron-collapse` adjusts the max-height/max-width of the collapsible element to show/hide
the content. So avoid putting padding/margin/border on the collapsible directly,
and instead put a div inside and style that.
```html
```
### Styling
The following custom properties and mixins are available for styling:
| Custom property | Description | Default |
| --- | --- | --- |
| `--iron-collapse-transition-duration` | Animation transition duration | `300ms` |
See: [Documentation](https://www.webcomponents.org/element/@polymer/iron-collapse),
[Demo](https://www.webcomponents.org/element/@polymer/iron-collapse/demo/demo/index.html).
## Usage
### Installation
```
npm install --save @polymer/iron-collapse
```
### In an html file
```html
```
### In a Polymer 3 element
```js
import {PolymerElement, html} from '@polymer/polymer';
import '@polymer/iron-collapse/iron-collapse.js';
class SampleElement extends PolymerElement {
static get template() {
return html`
`;
}
}
customElements.define('sample-element', SampleElement);
```
## Contributing
If you want to send a PR to this element, here are
the instructions for running the tests and demo locally:
### Installation
```sh
git clone https://github.com/PolymerElements/iron-collapse
cd iron-collapse
npm install
npm install -g polymer-cli
```
### Running the demo locally
```sh
polymer serve --npm
open http://127.0.0.1:/demo/
```
### Running the tests
```sh
polymer test --npm
```
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