Fix IE11

demo/index.html

@@ -49,12 +49,12 @@
           mirror: true
         });
 
-        document.addEventListener('aos:in', ({ detail }) => {
-          console.log('in!', detail);
+        document.addEventListener('aos:in', function(e) {
+          console.log('in!', e.detail);
         });
 
         window.addEventListener('scroll', function() {
-          scrollCounter.innerHTML = window.scrollY;
+          scrollCounter.innerHTML = window.pageYOffset;
         });
       }
     </script>

src/js/helpers/handleScroll.js

@@ -1,3 +1,5 @@
+import detect from './detector';
+
 /**
  * Adds multiple classes on node
  * @param {DOMNode} node
@@ -15,9 +17,17 @@ const removeClasses = (node, classes) =>
   classes && classes.forEach(className => node.classList.remove(className));
 
 const fireEvent = (eventName, data) => {
-  const customEvent = new CustomEvent(eventName, {
-    detail: data
-  });
+  let customEvent;
+
+  if (detect.ie11()) {
+    customEvent = document.createEvent('CustomEvent');
+    customEvent.initCustomEvent(eventName, true, true, { detail: data });
+  } else {
+    customEvent = new CustomEvent(eventName, {
+      detail: data
+    });
+  }
+
   return document.dispatchEvent(customEvent);
 };
 

src/js/helpers/prepare.js

@@ -11,10 +11,9 @@ const prepare = function($elements, options) {
     const customClassNames =
       options.useClassNames && el.node.getAttribute('data-aos');
 
-    const animatedClassNames = [
-      options.animatedClassName,
-      ...(customClassNames && customClassNames.split(' '))
-    ].filter(className => typeof className === 'string');
+    const animatedClassNames = [options.animatedClassName]
+      .concat(customClassNames ? customClassNames.split(' ') : [])
+      .filter(className => typeof className === 'string');
 
     if (options.initClassName) {
       el.node.classList.add(options.initClassName);