ajax上传 图片/文件

$("#datatable").on("change",'input[type=file]',function() {
    var formdata = new FormData(); 
    var v_this = $(this); 
    var fileObj = v_this.get(0).files; 
    url = ".."; 
    formdata.append("brand_img", fileObj[0]); 
    formdata.append("id", $(this).attr("data-id")); 
 
    jQuery.ajax({ 
        url : url, 
        type : 'post', 
        data : formdata, 
        cache : false, 
        contentType : false, 
        processData : false, 
        dataType : "json", 
        success : function(data) { 
            //yourcode..
        } 
    }); 
    return false; 
});