怎么用javascript实现自定义事件功能

function doSomething(){  A();  B();}

//1、创建事件var clickElem = new Event("clickElem");//2、注册事件监听器elem.addEventListener("clickElem",function(e){  //干点事})//3、触发事件elem.dispatchEvent(clickElem);

import b from "./b"import c from "./c"var a = document.getElementById("a");a.addEventListener("click",function(e){  var clickA = new Event("clickA");  document.dispatchEvent(clickA);});

var b = document.getElementById("b");document.addEventListener("clickA",function(e){  b.innerHTML = "(128,345)";})

var c = document.getElementById("c");document.addEventListener("clickA",function(e){  c.innerHTML = "你点了A";})

import loadImage from "./loadImage"import loadMusic from "./loadMusic"import initScene from "./initScene"  var start = document.getElementById("start");start.addEventListener("click",function(e){  console.log("游戏开始！");  document.dispatchEvent(new Event("gameStart"));})

// 加载图片document.addEventListener("gameStart",function(){  console.log("加载图片...");  setTimeout(function(){    console.log("加载图片完成");    document.dispatchEvent(new Event("loadImageSuccess"));  },1000);});

//加载音乐document.addEventListener("gameStart",function(){  console.log("加载音乐...");  setTimeout(function(){    console.log("加载音乐完成");    document.dispatchEvent(new Event("loadMusicSuccess"));  },2000);});

//渲染场景document.addEventListener("loadImageSuccess",function(e){  console.log("使用图片创建场景...");  setTimeout(function(){    console.log("创建场景完成");  },2000)});//渲染音效document.addEventListener("loadMusicSuccess",function(e){  console.log("使用音乐创建音效...");  setTimeout(function(){    console.log("创建音效完成");  },500)});

var event = new CustomEvent('myEvent', { 'dataName': dataContent });document.dispatchEvent(event);

document.addEventListener("myEvent",function(e){  console.log(e.dataName);})