@lion/collapsible

Collapsible

lion-collapsible is a combination of a button (the invoker), a chunk of 'extra content', and an animation that is used to disclose the extra content. There are two slots available respectively; invoker to specify collapsible invoker and content for the extra content of the collapsible.

import { html } from 'lit-html';

import './lion-collapsible.js';
import './demo/custom-collapsible.js';
import './demo/applyDemoCollapsibleStyles.js';

export default {
  title: 'Others/Collapsible',
};

export const main = () => html`
  <lion-collapsible>
    <button slot="invoker">More about cars</button>
    <div slot="content">
      Most definitions of cars say that they run primarily on roads, seat one to eight people, have
      four tires, and mainly transport people rather than goods.
    </div>
  </lion-collapsible>
`;

Features

• Use opened or toggle() to render default open
• invoker slot can be custom template e.g. lion-button or native button with custom styling
• Observe the state with the help of @opened-changed event
• show() and hide() are helper methods to hide or show the content from outside

How to use

Installation

npm i --save @lion/collapsible

import { LionCollapsible } from '@lion/collapsible';
// or
import '@lion/collapsible/lion-collapsible.js';

Usage

<lion-collapsible>
  <button slot="invoker">Invoker Text</button>
  <div slot="content">
    Extra content
  </div>
</lion-collapsible>

Examples

Default open

Add the opened attribute to keep the component default open.

export const defaultOpen = () => html`
  <lion-collapsible opened>
    <button slot="invoker">More about cars</button>
    <div slot="content">
      Most definitions of cars say that they run primarily on roads, seat one to eight people, have
      four tires, and mainly transport people rather than goods.
    </div>
  </lion-collapsible>
`;

Methods

There are the following methods available to control the extra content for the collapsible.

• toggle(): toggle the extra content
• show(): show the extra content
• hide(): hide the extra content

export const methods = () => html`
  <lion-collapsible id="car-collapsible">
    <button slot="invoker">More about cars</button>
    <div slot="content">
      Most definitions of cars say that they run primarily on roads, seat one to eight people, have
      four tires, and mainly transport people rather than goods.
    </div>
  </lion-collapsible>
  <section style="margin-top:16px">
    <button @click=${() => document.querySelector('#car-collapsible').toggle()}>
      Toggle content
    </button>
    <button @click=${() => document.querySelector('#car-collapsible').show()}>
      Show content
    </button>
    <button @click=${() => document.querySelector('#car-collapsible').hide()}>
      Hide content
    </button>
  </section>
`;

Events

lion-collapsible fires an event on invoker click to notify the component's current state. It is useful for analytics purposes or to perform some actions while expanding and collapsing the component.

• @opened-changed: triggers when collapsible either gets opened or closed

export const events = () => html`
  <div class="demo-custom-collapsible-state-container">
    <strong id="collapsible-state"></strong>
  </div>
  <lion-collapsible
    @opened-changed=${e => {
      const collapsibleState = document.getElementById('collapsible-state');
      collapsibleState.innerText = `Opened: ${e.target.opened}`;
    }}
  >
    <button slot="invoker">More about cars</button>
    <div slot="content">
      Most definitions of cars say that they run primarily on roads, seat one to eight people, have
      four tires, and mainly transport people rather than goods.
    </div>
  </lion-collapsible>
`;

Custom Invoker Template

A custom template can be specified to the invoker slot. It can be any button or custom component which mimics the button behavior for better accessibility support. In the below example, lion-button and native button with styling is used as a collapsible invoker.

export const customInvokerTemplate = () => html`
  <lion-collapsible>
    <button class="demo-custom-collapsible-invoker" slot="invoker">
      MORE ABOUT CARS
    </button>
    <div slot="content">
      Most definitions of cars say that they run primarily on roads, seat one to eight people, have
      four tires, and mainly transport people rather than goods.
    </div>
  </lion-collapsible>
  <lion-collapsible style="margin-top:16px;">
    <lion-button slot="invoker">More about cars</lion-button>
    <div slot="content">
      Most definitions of cars say that they run primarily on roads, seat one to eight people, have
      four tires, and mainly transport people rather than goods.
    </div>
  </lion-collapsible>
`;

Extended collapsible with animation

LionCollapsible can easily be extended to add more features in the component, for example, animation.

export const customAnimation = () => html`
  <div class="demo-custom-collapsible-container">
    <div class="demo-custom-collapsible-body">
      A motorcycle, often called a motorbike, bike, or cycle, is a two- or three-wheeled motor
      vehicle.
    </div>
    <custom-collapsible>
      <button class="demo-custom-collapsible-invoker" slot="invoker">
        MORE ABOUT MOTORCYCLES
      </button>
      <div slot="content">
        Motorcycle design varies greatly to suit a range of different purposes: long distance
        travel, commuting, cruising, sport including racing, and off-road riding. Motorcycling is
        riding a motorcycle and related social activity such as joining a motorcycle club and
        attending motorcycle rallies.
      </div>
    </custom-collapsible>
  </div>
  <div class="demo-custom-collapsible-container">
    <div class="demo-custom-collapsible-body">
      A car (or automobile) is a wheeled motor vehicle used for transportation.
    </div>
    <custom-collapsible opened>
      <button class="demo-custom-collapsible-invoker" slot="invoker">
        MORE ABOUT CARS
      </button>
      <div slot="content">
        Most definitions of cars say that they run primarily on roads, seat one to eight people,
        have four tires, and mainly transport people rather than goods.
      </div>
    </custom-collapsible>
  </div>
`;

Use _showAnimation and _hideAnimation methods to customize open and close behavior. Check the full example for the custom-collapsible here.

_showAnimation({ contentNode }) {
    const expectedHeight = await this.__calculateHeight(contentNode);
    contentNode.style.setProperty('opacity', '1');
    contentNode.style.setProperty('padding', '12px 0');
    contentNode.style.setProperty('max-height', '0px');
    await new Promise(resolve => requestAnimationFrame(() => resolve()));
    contentNode.style.setProperty('max-height', expectedHeight);
    await this._waitForTransition({ contentNode });
}

_hideAnimation({ contentNode }) {
    if (this._contentHeight === '0px') {
      return;
    }
    ['opacity', 'padding', 'max-height'].map(prop => contentNode.style.setProperty(prop, 0));
    await this._waitForTransition({ contentNode });
}