upload

@@ -16,6 +16,8 @@ var $result,
     $upload,
     $filename;
 
+var uping;
+
 var num,
     inter,
     callback;
@@ -27,8 +29,12 @@ $upload = $('#yoho-upload');
 $filename = $upload.find('.file-name');
 
 function up(opt) {
+    if (uping) {
+        return;
+    }
+
     $filename.click();
-    if (opt) {
+    if (opt && typeof opt.callback === 'function') {
         callback = opt.callback;
     } else {
         callback = '';
@@ -40,22 +46,24 @@ function getResponse(cb) {
     inter = setInterval(function() {
         var res = $result[0].contentDocument.body.innerText || '';
 
+        if (num > 20 || res) {
+            uping = false;
+            clearInterval(inter);
+        }
+
+        num++;
+
         if (res) {
             $result[0].contentDocument.body.innerText = '';
             if (cb) {
                 return cb($.parseJSON(res));
             }
         }
-
-        if (num > 20 || res) {
-            clearInterval(inter);
-        }
-
-        num++;
     }, 500);
 }
 
 $filename.change(function() {
+    uping = true;
     $upload.submit();
     getResponse(callback);
 });