Web Components Expansion Panel Overview

The Ignite UI for Web Components Expansion Panel is a lightweight accordion component which can be rendered in two states - collapsed or expanded. The expansion panel can be toggled using mouse click, or keyboard interactions.

Web Components Expansion Panel Example

Usage

First, you need to install the Ignite UI for Web Components by running the following command:

npm install igniteui-webcomponents

Before using the ExpansionPanel, you need to register it as follows:

import {defineComponents, IgcExpansionPanelComponent} from 'igniteui-webcomponents';

defineComponents(IgcExpansionPanelComponent);

For a complete introduction to the Ignite UI for Web Components, read the Getting Started topic.

The simplest way to start using the ExpansionPanel is as follows:

<igc-expansion-panel indicator-position="end">
  <span slot="title">Golden Retriever</span>
  <span slot="subtitle">Medium-large gun dog</span>
  <p>The Golden Retriever is a medium-large gun dog that retrieves shot waterfowl, such as ducks
  and upland game birds, during hunting and shooting parties.[3] The name "retriever" refers to the breed's ability
  to retrieve shot game undamaged due to their soft mouth. Golden retrievers have an instinctive love of water, and
  are easy to train to basic or advanced obedience standards.</p>
</igc-expansion-panel>

Binding to events

The Expansion Panel component raises the following events:

• igcClosed - Raised when the expansion panel is collapsed
• igcOpened - Raised when the expansion panel is expanded
• igcClosing - Raised when the expansion panel starts collapsing
• igcOpening - Raised when the expansion panel starts expanding

The following sample demonstrates how we can add some logic to our component to make it show/hide the subtitle depending on the current state of the panel.

We can do this by binding to the igcOpened and igcClosed event emitters:

Component Customization

The ExpansionPanel control allows all sorts of content to be added inside of its body. It can render input, charts and even other expansion panels!

The ExpansionPanel allows for easy customization of the header through the exposed title, subTitle and indicator slots.

Configuring the position of the expansion indicator can be done through the IndicatorPosition property of the Expansion Panel. The possible options are start, end or none.

The next code sample demonstrates how to configure the component’s button to go on the right side.

Recommended Elements for Slots

When slotting content into the title and subtitle slots, we recommend using <span> elements rather than heading elements (<h1>–<h6>). Heading elements carry built-in styling (such as font size, line height, and margins) that can interfere with the component’s intended typography and layout. Using a <span> gives you a neutral container that inherits the component’s styles cleanly.

The indicator slot is intended for icon-like content. We recommend using the <igc-icon> component for this purpose. Alternatively, if you don’t want to use an icon for the indicator, a <span> element can be used to display text, symbols, or emojis.

<igc-expansion-panel>
  <span slot="title">Golden Retriever</span>
  <span slot="subtitle">Medium-large gun dog</span>
  <igc-icon slot="indicator" name="arrow_forward"></igc-icon>
</igc-expansion-panel>

Keyboard Navigation

The Ignite UI for Web Components Expansion Panel keyboard navigation is compliant with W3C accessibility standards and convenient to use.

Key Combinations

• ALT + ↓ - expands the focused panel
• ALT + ↑ - collapses the focused panel
• SPACE/ENTER - toggle the expansion state of the focused panel

Styling

The ExpansionPanel component exposes several CSS parts, giving you full control over its style:

igc-expansion-panel {
  background-color: var(--ig-secondary-900);
  color: var(--ig-secondary-900-contrast);
}

igc-button::part(base) {
  color: var(--ig-secondary-900-contrast);
}

igc-button::part(base)::before {
  background-color: var(--ig-warn-500);
}

igc-expansion-panel::part(indicator) {
  color: var(--ig-warn-500);
}

igc-expansion-panel::part(header) {
  background-color: var(--ig-secondary-900);
}

igc-expansion-panel::part(title),
igc-expansion-panel::part(subtitle) {
  color: var(--ig-warn-500);
}

API References

Additional Resources

• Ignite UI for Web Components Forums
• Ignite UI for Web Components GitHub