Adds collapsible behavior to a target element
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README.md

Published on NPM Build status Published on webcomponents.org

<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.

<style>
  .collapse-content {
    padding: 15px;
    border: 1px solid #dedede;
  }
</style>

<iron-collapse>
  <div class="collapse-content">
    <div>Content goes here...</div>
  </div>
</iron-collapse>

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, Demo.

Usage

Installation

npm install --save @polymer/iron-collapse

In an html file

<html>
  <head>
    <script type="module">
      import '@polymer/iron-collapse/iron-collapse.js';
    </script>
  </head>
  <body>
    <iron-collapse id="collapse">
      <div>Content goes here...</div>
    </iron-collapse>
  </body>
</html>

In a Polymer 3 element

import {PolymerElement, html} from '@polymer/polymer';
import '@polymer/iron-collapse/iron-collapse.js';

class SampleElement extends PolymerElement {
  static get template() {
    return html`
      <iron-collapse id="collapse">
        <div>Content goes here...</div>
      </iron-collapse>
    `;
  }
}
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

git clone https://github.com/PolymerElements/iron-collapse
cd iron-collapse
npm install
npm install -g polymer-cli

Running the demo locally

polymer serve --npm
open http://127.0.0.1:<port>/demo/

Running the tests

polymer test --npm