一个简单的异步上传方法

<! DOCTYPE html>

< html>

< head>

< meta charset ="GB2312" >

< title> Insert title here </title >

< script type ="text/javascript" src= "jquery.js"></ script >

< script type ="text/javascript" >

$(document).ready( function (){

      $( "#i_1" ).load( function(){

             var url = $("#i_1" ).contents().find( "#pic").html();

             if (url != null){

                  $( "#tag_img" ).attr("src" ,url);

            }

      });

});

</ script>

</ head>

< body>

< img id= "tag_img" src = "" />

< form enctype ="multipart/form-data" action= "upload_pic.php" method ="post" target= "upload_target">

     <input type= "file" name ="img" class= "file" value ="" />

     <input type= "submit" name ="uploadimg" value= "上传" />

</ form>

< iframe id= "i_1" name = "upload_target"></ iframe >

</ body>

</ html>

重点：

1.form中的axtion="处理图片的有效页面"

2.form中的target="iframe的name属性值"

3.JS中必须要有可以等待iframe加载完后处理iframe返回过来的图片地址。