iframe模拟异步上传图片

<iframe id="uploadframe" width="0" height="0" style="display:none;" name="upload_target"></iframe>



<form id="uploadpic" target="upload_target" enctype="multipart/form-data" method="post" action="" style="display: none;">



<input type="file" name="uploadImg" id="uploadImg">



</form>



$(function(){



$("#uploadImg").change(function(){



   if($(this).val() && checkFile('uploadImg')){



​       $('#uploadpic').submit();



       $(this).val('');​



       return true;



       //$('#uploadpic').submit();​



   }



   return false;



});



});



function checkFile(id)



{



    extensions = 'jpg,gif,png,jpeg';



    var path = document.getElementByIdx_x_x_x_x_x_x(id).value;



    var ext = getExt(path);



    var re = new RegExp("(^|\\s|,)" + ext + "($|\\s|,)", "ig");



    if(extensions != '' && (re.exec(extensions) == null || ext == '')) {



        $.messager.alert("对不起，只能上传jpg, jpeg, png, gif类型的图片!");



        $('#'+id).val('');



        return false;



    }



    //showLoading();



    return true;



}



function getExt(path) {



    return path.lastIndexOf('.') == -1 ? '' : path.substr(path.lastIndexOf('.') + 1, path.length).toLowerCase();



}