js实现上传图片及时预览_javascript技巧

先为大家分享一段关于js图片预览的代码，兼容火狐和谷歌浏览器

 /* 案例展示图片预览 */$(function(){  $("#file0").bind("change",function(){     clickupLoad();  });});function clickupLoad(){   var imgObject = document.getElementById('file0');  var getImageSrc = getFullPath(imgObject); // 本地路径  var srcs = window.URL.createObjectURL(imgObject.files[0]);  var pos = getImageSrc.lastIndexOf(".");  var lastname = getImageSrc.substring(pos, getImageSrc.length) // 图片后缀]     if(srcs!=""){    $("#yulan2").attr("src",srcs);  }else{    alert("请选择一张图片");  }   }function getFullPath(obj) {  //得到图片的完整路径  if (obj)  {    if (window.navigator.userAgent.indexOf("MSIE") >= 1){      obj.select();      return document.selection.createRange().text;         }else if(window.navigator.userAgent.indexOf("Firefox") >= 1) {      if (obj.files) {        return window.URL.createObjectURL(obj.files[0]);      }      return obj.value;    }    return obj.value;  }}

实例代码实现js上传图片及时预览：

         <script type="text/javascript">          //图片上传预览  IE是用了滤镜。    function previewImage(file)    {     var MAXWIDTH = 260;      var MAXHEIGHT = 180;     var p = document.getElementById('preview');     if (file.files && file.files[0])     {       p.innerHTML ='
';       var img = document.getElementById('imghead');       img.onload = function(){        var rect = clacImgZoomParam(MAXWIDTH, MAXHEIGHT, img.offsetWidth, img.offsetHeight);        img.width = rect.width;        img.height = rect.height;//         img.style.marginLeft = rect.left+'px';        img.style.marginTop = rect.top+'px';       }       var reader = new FileReader();       reader.onload = function(evt){img.src = evt.target.result;}       reader.readAsDataURL(file.files[0]);     }     else //兼容IE     {      var sFilter='filter:progid:DXImageTransform.Microsoft.AlphaImageLoader(sizingMethod=scale,src="';      file.select();      var src = document.selection.createRange().text;      p.innerHTML = '
';      var img = document.getElementById('imghead');      img.filters.item('DXImageTransform.Microsoft.AlphaImageLoader').src = src;      var rect = clacImgZoomParam(MAXWIDTH, MAXHEIGHT, img.offsetWidth, img.offsetHeight);      status =('rect:'+rect.top+','+rect.left+','+rect.width+','+rect.height);      p.innerHTML = "
";     }    }    function clacImgZoomParam( maxWidth, maxHeight, width, height ){      var param = {top:0, left:0, width:width, height:height};      if( width>maxWidth || height>maxHeight )      {        rateWidth = width / maxWidth;        rateHeight = height / maxHeight;                 if( rateWidth > rateHeight )        {          param.width = maxWidth;          param.height = Math.round(height / rateWidth);        }else        {          param.width = Math.round(width / rateHeight);          param.height = maxHeight;        }      }             param.left = Math.round((maxWidth - param.width) / 2);      param.top = Math.round((maxHeight - param.height) / 2);      return param;    }《script》      
  
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以上就是本文的全部内容，希望对大家学习javascript程序设计有所帮助。