                        課程
                    
                        /前端開發(fā)
                        
                            /JavaScript
                        
                        /JS動(dòng)畫效果

代碼寫入for循環(huán)就沒有效果，把每一項(xiàng)單獨(dú)寫出來能出現(xiàn)效果，這是為什么？

在window.onload部分，遍歷img標(biāo)簽時(shí)，把每個(gè)標(biāo)簽單獨(dú)寫動(dòng)畫能出現(xiàn)動(dòng)態(tài)效果，但合成for循環(huán)就不行。

<!DOCTYPE?html>
<html?lang="en">
<head>
????<meta?charset="UTF-8">
????<title>動(dòng)畫案例</title>
????<style>
?div{
????????????margin:?20px;
????????????padding:?20px;
????????}
????????img{
????????????width:?130px;
????????????height:?100px;
????????????margin:?2px;
????????????opacity:?1;
????????????filter:?alpha(opacity:100);
????????????position:?relative;
????????????top:20px;
????????????display:?inline-block;
????????}
????</style>
????<script>
?window.onload?=?function?()?{
?var?allImgs?=?document.getElementsByTagName('img');
?//for循環(huán)中不能出現(xiàn)動(dòng)態(tài)效果
?for(var?i=0;i<allImgs.length;i++){
?allImgs[i].timer?=?null;
?allImgs[i].onmouseover?=?function?()?{
?onMove(allImgs[i],{'top':-20,'opacity':0},function?()?{
?allImgs[i].style.top?=?'30px';
?onMove(allImgs[i],{'top':20,'opacity':100});
????????????????????});
????????????????}
????????????}
?/*
????????????//每一項(xiàng)寫出來能出現(xiàn)動(dòng)態(tài)效果
????????????allImgs[0].timer?=?null;
????????????allImgs[0].onmouseover?=?function?()?{
????????????????onMove(allImgs[0],{'top':-20,'opacity':0},function?()?{
????????????????????allImgs[0].style.top?=?'30px';
????????????????????onMove(allImgs[0],{'top':20,'opacity':100});
????????????????});
????????????}

????????????allImgs[1].timer?=?null;
????????????allImgs[1].onmouseover?=?function?()?{
????????????????onMove(allImgs[1],{'top':-20,'opacity':0},function?()?{
????????????????????allImgs[1].style.top?=?'35px';
????????????????????onMove(allImgs[1],{'top':20,'opacity':100});
????????????????});
????????????}
????????????*/
?}
?</script>
</head>
<body>
<div?id="div1">
????<img?src="http://img1.sycdn.imooc.com//57466d580001d46806000338-240-135.jpg"?class="imgs">
????<img?src="http://img1.sycdn.imooc.com//57466d580001d46806000338-240-135.jpg"?class="imgs">
</div>
</body>
</html>

<script>
?function?onMove(obj,json,fn)?{
?clearInterval(obj.timer);
?obj.timer?=?setInterval(function?()?{
?var?flag?=?true;????//設(shè)置flag，標(biāo)注是否所有屬性改變完全
?for(var?attr?in?json){
?if(attr?==?'opacity'){
?var?icur?=?Math.round(100*getStyle(obj,attr));
????????????????}else?{
?var?icur?=?getStyle(obj,attr);
????????????????}
?if(icur!=json[attr]){
?flag?=?false;
?//var?speed?=?(json[attr]>icur)?10:-10;???//變化速度
?var?speed?=?(json[attr]-icur)/8;
?speed?=?(speed>0)?Math.ceil(speed):Math.floor(speed);
?if(attr?==?'opacity'){
?obj.style[attr]?=?(icur?+?speed)/100;
?obj.style['filter']?=?'alpha(opacity:'+(icur+speed)+')';
????????????????????}else?{
?obj.style[attr]?=?icur?+?speed?+?'px';
????????????????????}
????????????????}
????????????}
?if(flag?==?true){
?clearInterval(obj.timer);
?if(fn){
?fn();
????????????????}
????????????}

????????},30)
????}
?function?getStyle(obj,attr)?{
?//返回屬性值，int或者float
?if(document.currentStyle){
?var?res?=?currentStyle(obj)[attr];?//IE
?}
?else?{
?var?res?=??getComputedStyle(obj,null)[attr];?//Firefox
?}
?if(attr?==?'opacity'){
?return?parseFloat(res);
????????}else{
?return?parseInt(res);
????????}
????}
</script>