详解原生JS动态添加和删除类

let element = document.getElementById("box");

let attr = document.createAttribute("class");
attr.nodeValue = "className";
el.setAttributeNode(attr)

	
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按钮3
	
按钮4

let myEventUtil = {
	// 添加监听事件
	addEvent (element, type, handler) {
		if (element.addEventListener) {
			element.addEventListener(type, handler, false);
		} else if (element.attach){ // ie
			element.attach("on"+ type, handler);
		} else {
			element['on' + type] = handler;
		}
	},
	getTarget (event) {
		let event = event || window.event;
		return event.target || event.srcElement;
	}
}
let my$ = id => document.getElementById(id);

let btnGroup = my$(“btn-group”);
myEventUtil.addEvent(btnGroup, 'on', function (ev) {
	// 给所有的 btn 都移除激活的类 btn-active
	// console.log(this) ==> 是一个dom元素 btnGroup 
	// 可以通过 el.children[i]拿到具体的子元素
	// 拿到子元素了可以通过 el.classList.remove("className") 删除类
	// el.classList.add("className") 来添加类
	
	// 删除类
	let len = this.children.length;
	for (let i = 0; i