javascript - 类型错误 : listener must be a function

Question

我在 WeakMap 中存储了一个事件监听器，并在检索函数以将其从 EventEmitter 中删除时抛出此错误:

TypeError: listener must be a function

我只是想不通问题是什么:

var EventEmitter = require('events').EventEmitter;

var listeners = new WeakMap();
var eventEmitterA = new EventEmitter();
var eventEmitterB = new EventEmitter();

eventEmitterA.on('open', (obj) => {
  function stuff() { /* ... */ }

  listeners.set(obj, stuff);

  eventEmitterB.on('stuff', stuff);
});

eventEmitterA.on('close', (obj) => {
  var listener = listeners.get(obj);

  console.log(typeof listener); // logs "function"

  eventEmitterB.removeListener(listener);
});


var someObject = {some: 'object'};

eventEmitterA.emit('open', someObject);
eventEmitterA.emit('close', someObject);

Answer 1

eventEmitterB.removeListener(listener);

应该是

eventEmitterB.removeListener('stuff', listener);

removeListener 有两个参数，函数应该是第二个参数，因此您将函数作为处理程序的名称传递，并将 undefined 作为处理程序传递。