content/snippets/react/s/accordion.md
---
title: Collapsible accordion
type: snippet
language: react
tags: [components,children,state]
cover: orange-wedges
dateModified: 2021-10-13
---
Renders an accordion menu with multiple collapsible content elements.
- Define an `AccordionItem` component, that renders a `<button>`. The button updates the component and notifies its parent via the `handleClick` callback.
- Use the `isCollapsed` prop in `AccordionItem` to determine its appearance and set its `className`.
- Define an `Accordion` component. Use the `useState()` hook to initialize the value of the `bindIndex` state variable to `defaultIndex`.
- Filter `children` to remove unnecessary nodes except for `AccordionItem` by identifying the function's name.
- Use `Array.prototype.map()` on the collected nodes to render the individual collapsible elements.
- Define `changeItem`, which will be executed when clicking an `AccordionItem`'s `<button>`.
- `changeItem` executes the passed callback, `onItemClick`, and updates `bindIndex` based on the clicked element.
```css
.accordion-item.collapsed {
display: none;
}
.accordion-item.expanded {
display: block;
}
.accordion-button {
display: block;
width: 100%;
}
```
```jsx
const AccordionItem = ({ label, isCollapsed, handleClick, children }) => {
return (
<>
<button className="accordion-button" onClick={handleClick}>
{label}
</button>
<div
className={`accordion-item ${isCollapsed ? 'collapsed' : 'expanded'}`}
aria-expanded={isCollapsed}
>
{children}
</div>
</>
);
};
const Accordion = ({ defaultIndex, onItemClick, children }) => {
const [bindIndex, setBindIndex] = React.useState(defaultIndex);
const changeItem = itemIndex => {
if (typeof onItemClick === 'function') onItemClick(itemIndex);
if (itemIndex !== bindIndex) setBindIndex(itemIndex);
};
const items = children.filter(item => item.type.name === 'AccordionItem');
return (
<>
{items.map(({ props }) => (
<AccordionItem
isCollapsed={bindIndex !== props.index}
label={props.label}
handleClick={() => changeItem(props.index)}
children={props.children}
/>
))}
</>
);
};
ReactDOM.createRoot(document.getElementById('root')).render(
<Accordion defaultIndex="1" onItemClick={console.log}>
<AccordionItem label="A" index="1">
Lorem ipsum
</AccordionItem>
<AccordionItem label="B" index="2">
Dolor sit amet
</AccordionItem>
</Accordion>
);
```