//检测文件大小和类型

 function fileChange(target){

 //检测上传文件的类型

 if(!(/(?:jpg|gif|png|jpeg)$/i.test(target.value))) {

 alert("只允许上传jpg|gif|png|jpeg格式的图片");

 if(window.ActiveXObject) {//for IE

 target.select();//select the file ,and clear selection

 document.selection.clear();

 } else if(window.opera) {//for opera

 target.type="text";target.type="file";

 } else target.value="";//for FF,Chrome,Safari

 return;

 } else {

 return; //alert("ok");//or you can do nothing here.

 }

 //检测上传文件的大小

 var isIE = /msie/i.test(navigator.userAgent) && !window.opera;

 var fileSize = 0;

 if (isIE && !target.files){

 var filePath = target.value;

 var fileSystem = new ActiveXObject("Scripting.FileSystemObject");

 var file = fileSystem.GetFile (filePath);

 fileSize = file.Size;

 } else {

 fileSize = target.files[0].size;

 }

 var size = fileSize / 1024;

 if(size>(500)){

 alert("文件大小不能超过500KB");

 if(window.ActiveXObject) {//for IE

 target.select();//select the file ,and clear selection

 document.selection.clear();

 } else if(window.opera) {//for opera

 target.type="text";target.type="file";

 } else {

 target.value="";//for FF,Chrome,Safari

 }

 return;

 }else{

 return;

 }

 }