Merge pull request #9 from chrisbeach/master

Rewrite javascript Promise as callback for IE compatibility

assets/javascripts/discourse/initializers/preview-edits.js.es6

@@ -91,11 +91,11 @@ export default {
       _init() {
         const topic = this.get('topic');
         if (topic.get('thumbnails')) {
-          testImageUrl(topic.get('thumbnails.normal')).then(function(result){
-            if (result === 'error') {
+          testImageUrl(topic.get('thumbnails.normal'), function(imageLoaded) {
+            if (!imageLoaded) {
               topic.set('thumbnails', null)
             }
-          })
+          });
         }
       },
 

assets/javascripts/lib/test-image-url.js.es6

@@ -1,20 +1,18 @@
-var testImageUrl = function(url) {
-  return new Promise(function (resolve, reject) {
-    let timeout = 5000;
-    let timer, img = new Image();
-    img.onerror = img.onabort = function () {
-      clearTimeout(timer);
-      resolve("error");
-    };
-    img.onload = function () {
-      clearTimeout(timer);
-      resolve("success");
-    };
-    timer = setTimeout(function () {
-      resolve("error");
-    }, timeout);
-    img.src = url;
-  });
-}
+var testImageUrl = function(url, callback) {
+  let timeout = 5000;
+  let timer, img = new Image();
+  img.onerror = img.onabort = function () {
+    clearTimeout(timer);
+    callback(false);
+  };
+  img.onload = function () {
+    clearTimeout(timer);
+    callback(true);
+  };
+  timer = setTimeout(function () {
+    callback(false);
+  }, timeout);
+  img.src = url;
+};
 
 export default testImageUrl