5.ajax提交文件表单

<form action="" method="post" enctype="multipart/form-data" id="form_id2" >

            <input type="file" name="imagename" id="imagename2" />

 </form>

var form   = new FormData(document.getElementById("form_id2"));

$.ajax({url:"upload.class.php",type:"post",data:form,processData:false,contentType:false,success: function(data1){ },});