原生JavaScript實現(xiàn)的簡單放大鏡效果示例

更新時間：2018年02月07日 14:36:33 作者：karenYin0828

這篇文章主要介紹了原生JavaScript實現(xiàn)的簡單放大鏡效果,涉及javascript事件響應(yīng)及頁面元素屬性動態(tài)操作相關(guān)實現(xiàn)技巧,需要的朋友可以參考下

本文實例講述了原生JavaScript實現(xiàn)的簡單放大鏡效果。分享給大家供大家參考，具體如下：

原理： 其實所謂的放大就是準備兩張一樣的圖片，除大小不一樣。鼠標(biāo)移動到不同位置，將會顯示大圖片對應(yīng)的圖片內(nèi)容。

完整代碼：

<!DOCTYPE html>
<html lang="en">
<head>
 <meta charset="UTF-8">
 <title>放大鏡效果</title>
</head>
<body>
 <div id="wrap" style="position: relative;width: 900px;margin: 0 auto;text-align: center;">
  <div id="smallImg" style="width: 400px;height: 400px; position: relative;z-index: 1;">
   <img src="small.jpg" style="width: 400px;height: 400px;"/>
   <span id="filter" style="width: 200px;height: 200px;background-color: blue;opacity: 0.1;position: absolute;top: 0;left: 0; z-index: 2;cursor: move;display: none;">
   <span>
  </div>
  <div id="bigImg" style="width: 400px;height: 400px;overflow: hidden;position: absolute;right: 0px;top: 0;display: none;">
   <img src="large.jpg" style="width: 800px;height:800px; position: absolute;left: 0;top: 0;">
  </div>
 </div>
 <script type="text/javascript">
  var filter = document.getElementById('filter');
  var smallImg = document.getElementById('smallImg');
  var bigImg = document.getElementById('bigImg');
  var wrap = document.getElementById('wrap');
  var largeImgs = bigImg.getElementsByTagName('img')[0];
  smallImg.onmouseover = function(){
   bigImg.style.display = "inline-block";
   filter.style.display = "inline-block";
  }
  smallImg.onmousemove = function(event){
   var event = event || window.event;
   var mouseleft = event.clientX - wrap.offsetLeft;
   var mousetop = event.clientY - wrap.offsetTop;
   var left = mouseleft<smallImg.offsetWidth/4?0:mouseleft>smallImg.offsetWidth*3/4?smallImg.offsetWidth/2:(mouseleft - filter.offsetWidth/2);
   var top = mousetop<smallImg.offsetHeight/4?0:mousetop>smallImg.offsetHeight*3/4?smallImg.offsetHeight/2:(mousetop - filter.offsetWidth/2);
   filter.style.left = left + "px";
   filter.style.top = top +"px";
   largeImgs.style.left = "-" +　left*bigImg.offsetWidth/smallImg.offsetWidth + "px";
   largeImgs.style.top = "-" +　top*bigImg.offsetHeight/smallImg.offsetHeight + "px";
  }
  smallImg.onmouseout = function(){
   bigImg.style.display = "none";
   filter.style.display = "none";
  }
 </script>
</body>
</html>

運行效果：