import ReactDOM from 'react-dom' ;

class SomeComponent {

  constructor(props) {
    // First, add this to your constructor
    this.handleClickOutside = this.handleClickOutside.bind(this);
  }

  componentWillMount() {
    document.addEventListener('mousedown', this.handleClickOutside, false); 
  }

  // Unbind event on unmount to prevent leaks
  componentWillUnmount() {
    window.removeEventListener('mousedown', this.handleClickOutside, false);
  }

  handleClickOutside(event) {
    if(!ReactDOM.findDOMNode(this).contains(event.path[0])){
       console.log("OUTSIDE");
    }
  }
}

import { RefObject, useEffect } from 'react';

const useClickOutside = <T extends HTMLElement>(ref: RefObject<T>, fn: () => void) => {
    useEffect(() => {
        const element = ref?.current;
        function handleClickOutside(event: Event) {
            if (element && !element.contains(event.target as Node | null)) {
                fn();
            }
        }
        document.addEventListener('mousedown', handleClickOutside);
        return () => {
            document.removeEventListener('mousedown', handleClickOutside);
        };
    }, [ref]);
};

export default useClickOutside;

2021更新：

自从我添加这个响应以来，已经有一段时间了，而且由于它似乎仍然引起了一些兴趣，我想我会将它更新到更新的React版本。2021，我会这样写这个组件：

import React, { useState } from "react";
import "./DropDown.css";

export function DropDown({ options, callback }) {
    const [selected, setSelected] = useState("");
    const [expanded, setExpanded] = useState(false);

    function expand() {
        setExpanded(true);
    }

    function close() {
        setExpanded(false);
    }

    function select(event) {
        const value = event.target.textContent;
        callback(value);
        close();
        setSelected(value);
    }

    return (
        <div className="dropdown" tabIndex={0} onFocus={expand} onBlur={close} >
            <div>{selected}</div>
            {expanded ? (
                <div className={"dropdown-options-list"}>
                    {options.map((O) => (
                        <div className={"dropdown-option"} onClick={select}>
                            {O}
                        </div>
                    ))}
                </div>
            ) : null}
        </div>
    );
}

原始答案（2016）：

以下是最适合我的解决方案，无需将事件附加到容器：

某些HTML元素可以具有所谓的“焦点”，例如输入元素。当这些元素失去焦点时，它们也会对模糊事件做出响应。

要使任何元素具有焦点的能力，只需确保其tabindex属性设置为-1以外的任何值。在常规HTML中，这是通过设置tabindex属性实现的，但在React中，必须使用tabindex（注意大写I）。

您也可以通过JavaScript使用element.setAttribute（'tabindex'，0）执行此操作

这就是我用来制作自定义下拉菜单的原因。

var DropDownMenu = React.createClass({
    getInitialState: function(){
        return {
            expanded: false
        }
    },
    expand: function(){
        this.setState({expanded: true});
    },
    collapse: function(){
        this.setState({expanded: false});
    },
    render: function(){
        if(this.state.expanded){
            var dropdown = ...; //the dropdown content
        } else {
            var dropdown = undefined;
        }
        
        return (
            <div className="dropDownMenu" tabIndex="0" onBlur={ this.collapse } >
                <div className="currentValue" onClick={this.expand}>
                    {this.props.displayValue}
                </div>
                {dropdown}
            </div>
        );
    }
});

import { useClickAway } from "react-use";

useClickAway(ref, () => console.log('OUTSIDE CLICKED'));

在这里尝试了许多方法之后，我决定使用github.com/Pomax/react-onclickoutside，因为它非常完整。

我通过npm安装了模块并将其导入到组件中：

import onClickOutside from 'react-onclickoutside'

然后，在组件类中，我定义了handleClickOutside方法：

handleClickOutside = () => {
  console.log('onClickOutside() method called')
}

导出组件时，我将其包装在onClickOutside（）中：

export default onClickOutside(NameOfComponent)

就是这样。

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

const YourComponent: React.FC<ComponentProps> = (props) => {
  const ref = useRef<HTMLDivElement | null>(null);
  const [myState, setMyState] = useState(false);
  useEffect(() => {
    const listener = (event: MouseEvent) => {
      // we have to add some logic to decide whether or not a click event is inside of this editor
      // if user clicks on inside the div we dont want to setState
      // we add ref to div to figure out whether or not a user is clicking inside this div to determine whether or not event.target is inside the div
      if (
        ref.current &&
        event.target &&
        // contains is expect other: Node | null
        ref.current.contains(event.target as Node)
      ) {
        return;
      }
      // if we are outside
      setMyState(false);
    };
    // anytime user clics anywhere on the dom, that click event will bubble up into our body element
    // without { capture: true } it might not work
    document.addEventListener("click", listener, { capture: true });
    return () => {
      document.removeEventListener("click", listener, { capture: true });
    };
  }, []);

  return (
    <div  ref={ref}>
      ....
    </div>
  );
};