Detect click outside React component

The following solution uses ES6 and follows best practices for binding as well as setting the ref through a method.

To see it in action:

• Hooks Implementation
• Class Implementation After React 16.3
• Class Implementation Before React 16.3

Hooks Implementation:

import React, { useRef, useEffect } from "react";

/**
 * Hook that alerts clicks outside of the passed ref
 */
function useOutsideAlerter(ref) {
  useEffect(() => {
    /**
     * Alert if clicked on outside of element
     */
    function handleClickOutside(event) {
      if (ref.current && !ref.current.contains(event.target)) {
        alert("You clicked outside of me!");
      }
    }
    // Bind the event listener
    document.addEventListener("mousedown", handleClickOutside);
    return () => {
      // Unbind the event listener on clean up
      document.removeEventListener("mousedown", handleClickOutside);
    };
  }, [ref]);
}

/**
 * Component that alerts if you click outside of it
 */
export default function OutsideAlerter(props) {
  const wrapperRef = useRef(null);
  useOutsideAlerter(wrapperRef);

  return <div ref={wrapperRef}>{props.children}</div>;
}

Class Implementation:

After 16.3

import React, { Component } from "react";

/**
 * Component that alerts if you click outside of it
 */
export default class OutsideAlerter extends Component {
  constructor(props) {
    super(props);

    this.wrapperRef = React.createRef();
    this.handleClickOutside = this.handleClickOutside.bind(this);
  }

  componentDidMount() {
    document.addEventListener("mousedown", this.handleClickOutside);
  }

  componentWillUnmount() {
    document.removeEventListener("mousedown", this.handleClickOutside);
  }

  /**
   * Alert if clicked on outside of element
   */
  handleClickOutside(event) {
    if (this.wrapperRef && !this.wrapperRef.current.contains(event.target)) {
      alert("You clicked outside of me!");
    }
  }

  render() {
    return <div ref={this.wrapperRef}>{this.props.children}</div>;
  }
}

Before 16.3

import React, { Component } from "react";

/**
 * Component that alerts if you click outside of it
 */
export default class OutsideAlerter extends Component {
  constructor(props) {
    super(props);

    this.setWrapperRef = this.setWrapperRef.bind(this);
    this.handleClickOutside = this.handleClickOutside.bind(this);
  }

  componentDidMount() {
    document.addEventListener("mousedown", this.handleClickOutside);
  }

  componentWillUnmount() {
    document.removeEventListener("mousedown", this.handleClickOutside);
  }

  /**
   * Set the wrapper ref
   */
  setWrapperRef(node) {
    this.wrapperRef = node;
  }

  /**
   * Alert if clicked on outside of element
   */
  handleClickOutside(event) {
    if (this.wrapperRef && !this.wrapperRef.contains(event.target)) {
      alert("You clicked outside of me!");
    }
  }

  render() {
    return <div ref={this.setWrapperRef}>{this.props.children}</div>;
  }
}