原生JS 封装运动函数

在学原生JS之前，一直用jQuery 写运动，各种方便，但是不知其所以然，今天得空看了一个javascript 视频教程(这里不说了，以防广告的嫌疑)，只能用一个词语形容之后的感觉-------醍醐灌顶。

/*
- obj 指的是DOM对象
- json 指的是 CSS样式
- 例 startMove(oDiv,{width:100,height:100},function(){})
*/

function startMove(obj,json,fnEnd){
	clearInterval(obj.timer);	//先清除之前的定时器
	obj.timer = setInterval(function(){
		var bStop = true;	// 假设所有的值都到了
		for( var attr in json ){	//遍历json属性
			var cur = (attr == 'opacity') ? Math.round(parseFloat(getStyle(obj,attr))*100) : parseInt(getStyle(obj,attr)); //对opacity 特殊处理
			var speed = (json[attr] - cur)/6;
			speed = speed > 0 ? Math.ceil(speed) : Math.floor(speed); 	//speed 数字转化，防止不能到达目标的bug
			if( cur != json[attr]) bStop = false;	//如果没有达到目标值，则bStop设为false;
			if(attr == 'opacity'){
				obj.style.filter = 'alpha(opacity='+ (cur + speed) +')';
				obj.style.opacity = (cur + speed)/100;
			}else{
				obj.style[attr] = cur + speed + 'px';
			}
		}
		if(bStop){
			clearInterval(obj.timer);
			if(fnEnd) fnEnd();	 //执行回调函数
		}
	},30);
}

function getStyle(obj,name){
	return obj.currentStyle ? obj.currentStyle[name] : window.getComputedStyle(obj,null)[name];	//浏览器兼容性处理，注意getComputedStyle为只读属性
}

function getByClass(oParent,sClass){
	var aEle = oParent.getElementsByTagName('*');
	var aResult =[];
	var re = new RegExp('\\b' + sClass + '\\b','i');
	for(var i=0; i<aEle.length;i++ ){
		if(re.test(aEle[i].className)) aResult.push(aEle[i]);
	}
	return aResult;
}

此框架可以实现大部分的运动效果，下面是我写的仿百度首页幻灯片:

window.onload = function(){
	var oSlide = document.getElementById('slide');
	var asmallpicWrap = getByClass(oSlide,'smallpic')[0];
	var asmallUl = asmallpicWrap.getElementsByTagName('ul')[0];
	var abigpicWrap = getByClass(oSlide,'bigpic')[0];
	var asmallpic = asmallpicWrap.getElementsByTagName('li');
	var obigpic = abigpicWrap.getElementsByTagName('img');
	var oprev = getByClass(oSlide,'prev')[0];
	var onext = getByClass(oSlide,'next')[0];
	var nowIndex = 2;
	var now = 0;

	//大图切换
	for(var i=0; i<asmallpic.length;i++ ){
		asmallpic[i].index = i;
		asmallpic[i].onclick = function(){
			if(this.index == now) return ;
			now = this.index;
			tab();
		}
		asmallpic[i].onmouseover = function(){
			startMove(this,{'opacity':100});
		}
		asmallpic[i].onmouseout = function(){
			if(this.index!=now){
				startMove(this,{'opacity':60});
			}
			tab();
		}
	}

	function tab(){
		obigpic[now].style.zIndex = nowIndex++;
		for(var i=0; i<asmallpic.length;i++ ){
			startMove(asmallpic[i],{'opacity':60});
		}
		startMove(asmallpic[now],{'opacity':100});

		if(now <= 3){
			startMove(asmallUl,{'left':0});
		}else if(now == asmallpic.length-1){
			startMove(asmallUl,{'left':-(now-4)*asmallpic[0].offsetWidth});
		}else{
			startMove(asmallUl,{'left':-(now-3)*asmallpic[0].offsetWidth});
		}
	}

	//下一个
	oprev.onclick = function(){
		now--;
		if(now == -1 ){
			now = asmallpic.length-1
		}
		tab();
	}
	//上一个
	onext.onclick = function(){
		now++;
		if(now == asmallpic.length ){
			now = 0
		}
		tab();
	}

	var timer = setInterval(onext.onclick,3000);
	oSlide.onmouseover = function(){
		clearInterval(timer);
	}
	oSlide.onmouseout = function(){
		timer = setInterval(onext.onclick,3000);
	}

}

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