Check files uploaded by user

huningxin · huningxin · commit 2fd022949389 · 2017-09-27T16:48:18.000+08:00
diff --git a/doc/js_tutorials/js_assets/utils.js b/doc/js_tutorials/js_assets/utils.js
@@ -98,8 +98,11 @@ function Utils(errorOutputId) { // eslint-disable-line no-unused-vars
     this.addFileInputHandler = function(fileInputId, canvasId) {
         let inputElement = document.getElementById(fileInputId);
         inputElement.addEventListener('change', (e) => {
-            let imgUrl = URL.createObjectURL(e.target.files[0]);
-            self.loadImageToCanvas(imgUrl, canvasId);
+            let files = e.target.files;
+            if (files.length > 0) {
+                let imgUrl = URL.createObjectURL(files[0]);
+                self.loadImageToCanvas(imgUrl, canvasId);
+            }
         }, false);
     };
 
