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JS写的带Loading图片预加载效果的图片切换

时间：2013-08-29 08:47 来源：互联网作者：源码搜藏收藏推荐

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>带Loading效果的图片切换</title>
<style type="text/css"> 
body,div,ul,li{margin:0;padding:0;}
li{list-style:none;}
body{font:12px/1.5 \5fae\8f6f\96c5\9ed1;background:#000;}
#big{position:relative;width:800px;height:auto!important;height:400px;min-height:400px;margin:20px auto;text-align:center;}
#title{position:absolute;top:0;left:0;width:100%;background:#000;color:#fff;opacity:0.7;filter:alpha(opacity=70);font-size:20px;height:50px;}
#title span{padding:0 5px;line-height:50px;display:block;}
#big.loading{background:url(http://www.codefans.net/jscss/demoimg/201211/loading.gif) 50% 50% no-repeat;}
#masks_L,#masks_R{position:absolute;top:0;width:400px;height:100%;cursor:pointer;background:#f0f0f0;opacity:0;filter:alpha(opacity=0);}
#masks_L{left:0;}
#masks_R{right:0;}
#btn_L,#btn_R{position:absolute;top:50%;margin-top:-40px;width:39px;height:80px;overflow:hidden;cursor:pointer;text-indent:-9999px;background:url(http://www.codefans.net/jscss/demoimg/201211/btn.png) no-repeat;opacity:0;filter:alpha(opacity=0);}
#btn_L{left:10px;background-position:0 0;}
#btn_R{right:10px;background-position:-39px 0;}
</style>
<script type="text/javascript"> 
function getStyle(obj, attr){return obj.currentStyle ? obj.currentStyle[attr] : getComputedStyle(obj, null)[attr]}
window.onload = function ()
{
	var oBig = document.getElementById("big");
	var oMasksL = document.getElementById("masks_L");
	var oMasksR = document.getElementById("masks_R");
	var oBtnL = document.getElementById("btn_L");
	var oBtnR = document.getElementById("btn_R");
	var oTitle = document.getElementById("title");
	var oSpan = oTitle.getElementsByTagName("span")[0];
	var iNow = 0;
	var aData = [
		{"imgSrc" : "http://i.gtimg.cn/qqlive/images/20130729/i1375084160_1.jpg?max_age=604800", "title" : "美国农场的麦屯"},
		{"imgSrc" :"http://i.gtimg.cn/qqlive/images/20130727/i1374861550_1.jpg?max_age=604800", "title" : "日落美景。"},
		{"imgSrc" :"http://i.gtimg.cn/qqlive/images/20130726/i1374826505_1.jpg?max_age=604800", "title" : "童话般的乡间小道"},
		{"imgSrc" : "http://i.gtimg.cn/qqlive/images/20130807/i1375863226_1.jpg?max_age=604800", "title" : "欧洲环境真的很干净哦"},
		{"imgSrc" :"http://i.gtimg.cn/qqlive/images/20130731/i1375257641_1.jpg?max_age=604800", "title" : "神话巨石阵"}
	];
	
	oMasksL.onmouseover = oBtnL.onmouseover = function ()
	{
		startMove(oBtnL, "opacity", 100)
	};
	oMasksL.onmouseout = oBtnL.onmouseout = function ()
	{
		startMove(oBtnL, "opacity", 0)	
	};
	
	oMasksR.onmouseover = oBtnR.onmouseover = function ()
	{
		startMove(oBtnR, "opacity", 100)
	};
	oMasksR.onmouseout = oBtnR.onmouseout = function ()
	{
		startMove(oBtnR, "opacity", 0)	
	};
	
	function startMove(obj, attr, iTarget, fnEnd)
	{
		clearInterval(obj.timer);
		obj.timer = setInterval(function ()
		{
			doMove(obj, attr, iTarget, fnEnd)
		}, 30)	
	}
	
	function doMove(obj, attr, iTarget, fnEnd)
	{
		var iCur = parseFloat(getStyle(obj, attr));
		if (attr == "opacity")
		{
			iCur = parseInt(iCur * 100)
		}
		var iSpeed = (iTarget - iCur) / 5;
		iSpeed = iSpeed > 0 ? Math.ceil(iSpeed) : Math.floor(iSpeed);
		
		if (iTarget == iCur)
		{
			clearInterval(obj.timer);
			fnEnd && fnEnd();	
		}
		else
		{
			if (attr == "opacity")
			{
				obj.style.filter = "alpha(opacity = " + (iCur + iSpeed) + ")";
				obj.style.opacity = (iCur + iSpeed)	/ 100;
			}
			else
			{
				obj.style[attr] = iCur + iSpeed + "px";	
			}
		}
	}
	
	oBtnL.onclick = function ()
	{
		
		if (iNow <= 0)
		{
			alert("前面没有图片了！")
			return;
		}
		iNow--;
		loadImg();
	};
	
	oBtnR.onclick = function ()
	{
		if(iNow >= aData.length - 1)
		{
			alert("这是最后一张图片了！")
			return;
		}
		iNow++;
		loadImg();
	};
	
	loadImg();
	function loadImg()
	{
		oBig.className = "loading";
		oSpan.style.opacity = oTitle.style.height = 0;
		oSpan.style.filter = "alpha(opacity=0)";
		var oImg = oBig.getElementsByTagName("img");
		oImg[0] && oBig.removeChild(oImg[0]);
		var oTemp = document.createElement("img");
		var oNewImg = new Image();
		oNewImg.onload = function ()
		{
			oBig.className = "";			
			oTemp.src = this.src;
			oBig.appendChild(oTemp);
			oTemp.style.width = (oTemp.offsetWidth > 800 ? 800 : oTemp.offsetWidth) + "px";
			oBig.style.height = oTemp.style.height = oTemp.offsetHeight * oTemp.offsetWidth / oTemp.offsetWidth + "px";
			oSpan.innerHTML = aData[iNow].title;
			startMove(oTitle, "height", 50, function (){
				startMove(oTitle.childNodes[0], "opacity", 100)	
			})
		};
		oNewImg.src = aData[iNow].imgSrc
	}
};
</script>
</head>
<body>
	<div id="big">
    	<div id="masks_L"></div>
    	<div id="masks_R"></div>
        <div id="btn_L">左</div>
        <div id="btn_R">右</div>
        <div id="title"><span></span></div>
    </div>
</body>
</html>

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JS写的带Loading图片预加载效果的图片切换，智能判断是否是第一张或最后一张，带左右控制，点击左右箭头即可控制图片切换，兼容性也做的不错，而且代码精简，值得借鉴。由源码搜藏网整理,转载请注明出处https://www.codesocang.com/tx-pic/5514.html

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