[React] Close the menu component when click outside the menu

Most of the time, your components respond to events that occur within the component tree by defining their own handler or by accepting a handler defined by a parent component via props. Sometimes, this isn't enough. In this lesson, we'll rely on lifecycle hooks and good old fashioned DOM events to update state in a React component in response to an event that occurs outside of the component tree.

class Menu extends React.Component {
  constructor(props) {
    super(props)
    this.state = {
      isVisible: false
    }
    this.handleClickOutside = this.handleClickOutside.bind(this)
    this.toggleOptions = this.toggleOptions.bind(this)
    this.handleClick = this.handleClick.bind(this)
  }
  componentDidMount() {
    document.addEventListener('click', this.handleClickOutside)
  }

  componentWillUnmount() {
    document.removeEventListener('click', this.handleClickOutside)
  }

  handleClickOutside(evt) {
    if (!this.node.contains(evt.target)) {
      this.setState({ isVisible: false })
    }
  }

  toggleOptions(evt) {
    evt.preventDefault()
    this.setState(state => ({ isVisible: !state.isVisible }))
  }

  handleClick(choice, evt) {
    evt.preventDefault()
    this.props.handleMenuChoice(choice)
    this.setState({ isVisible: false })
  }

  render() {
    return (
      <div className="menu" ref={el => (this.node = el)}>
        <a href="#" onClick={this.toggleOptions}>
          Options
        </a>
        {this.state.isVisible
          ? <div className="menuContents">
              <a href="#" onClick={this.handleClick.bind(null, 'one')}>
                One
              </a>
              <a href="#" onClick={this.handleClick.bind(null, 'two')}>
                Two
              </a>
              <a href="#" onClick={this.handleClick.bind(null, 'three')}>
                Three
              </a>
              <a href="#" onClick={this.handleClick.bind(null, '')}>
                Clear Selection
              </a>
            </div>
          : null}
      </div>
    )
  }
}

The most important thing is how to detect whether user click outside the menu or not.

To do that, we use 'ref':

<div className="menu" ref={el => (this.node = el)}>

We assign the elememt to vairable 'this.node'.

console log the node:

<div class="menu">
    <a href="#">options</a>
</div>

When we click inside the menu, the 'evt.target' is the 'a' tag.

If we click outside the menu, then then 'evt.target' is the whole html tag.

Therefore, we can check:

if (!this.node.contains(evt.target)) {