js上传图片及预览功能实例分析

<img id="imgTag" style="height: 100px;" alt="" /><input type="file" />function DisplayImage(fileTag,imgTagId){var allowExtention=".jpg.png.gif";var extentionArr=fileTag.value.split('.');var extention = extentionArr[extentionArr.length-1];if(!(allowExtention.indexOf(extention)>-1)){alert("Please upload image!");}else{//for adveced broswer(the newest ie,chrome,ff)if(typeof(FileReader)!=="undefined"){var reader = new FileReader();reader.readAsDataURL(fileTag.files[0]);reader.onload = function(e){document.getElementById(imgTagId).setAttribute("src", e.target.result);}}else{//for(ie6)document.getElementById(imgTagId).setAttribute("src",fileTag.value);}}}