Collapsible accordion

OSCC · React, Components, Children, State · Oct 13, 2021

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.
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}
        />
      ))}
    </>
  );
};
.accordion-item.collapsed {
  display: none;
}

.accordion-item.expanded {
  display: block;
}

.accordion-button {
  display: block;
  width: 100%;
}
ReactDOM.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>,
  document.getElementById('root')
);

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