javascript - 编写一个 People 类，使其的实例具有事件绑定、触发事件、解除绑定功能。（实例可能监听多个不同的事件，也可以去除监听事件）

问题描述

问 题

/*
 * TODO
 *
 */

People.prototype.sayHi = function () {
    console.log('Hi, I am ' + this.name)
}

// 目标效果：

var jerry = new People('Jerry')
jerry.sayHi() // => 输出：'Hi, I am Jerry'

jerry.on('greeting', say)
jerry.on('greeting', say2)
jerry.emit('greeting', 'Hi') // => 输出：'Hi, nice meeting you.' 和 'Hi, nice meeting you, too'
jerry.off('greeting', say)
jerry.emit('greeting', 'Hi') // => 只输出：'Hi, nice meeting you, too'

function say (greeting) {
  console.log(greeting + ', nice meeting you.')
}

function say2 (greeting) {
  console.log(greeting + ', nice meeting you, too')

解决方案

         class People {
            constructor (name) {
                this.name = name
                this.events = {}
            }
            sayHi () {
                console.log('Hi, I am ' + this.name)
            }

            on (event, cbk) {
                // 利用数组储存同事件的所有回调
                (this.events[event] || (this.events[event] = [])).push(cbk)
            }

            off (event, cbk) {
                let eventArr = this.events[event]
                // 反向遍历,不至于删除数据之后,数组长度影响遍历
                for(let i=eventArr.length-1; i>=0; i--){
                    if(cbk === eventArr[i]){
                        eventArr.splice(i,1)
                    }
                }
            }

            emit (event, param){
                let eventArr = this.events[event]
                // 遍历同事件的所有回调,执行
                eventArr.forEach(function(cbk){
                    cbk(param)
                })
            }
        }


        var jerry = new People('Jerry')
        jerry.sayHi()
        
        jerry.on('greeting', say)
        jerry.on('greeting', say2)
        jerry.emit('greeting', 'Hi')
        jerry.off('greeting', say)
        jerry.emit('greeting', 'Hi')

        function say (greeting) {
          console.log(greeting + ', nice meeting you.')
        }
        function say2 (greeting) {
          console.log(greeting + ', nice meeting you, too')
        }

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