fix: disable mutation observing when not supported (michalsnik#405)

Disable mutation observing and display a message when MutationObserver is not supported by the browser.

Closes michalsnik#404

src/js/aos.js

@@ -10,7 +10,7 @@ import styles from './../sass/aos.scss';
 import throttle from 'lodash.throttle';
 import debounce from 'lodash.debounce';
 
-import observe from './libs/observer';
+import observer from './libs/observer';
 
 import detect from './helpers/detector';
 import handleScroll from './helpers/handleScroll';
@@ -139,13 +139,25 @@ const init = function init(settings) {
   // Create initial array with elements -> to be fullfilled later with prepare()
   $aosElements = elements();
 
+  /**
+   * Disable mutation observing if not supported
+   */
+  if (!options.disableMutationObserver && !observer.isSupported()) {
+    console.info(`
+      aos: MutationObserver is not supported on this browser,
+      code mutations observing has been disabled.
+      You may have to call "refreshHard()" by yourself.
+    `);
+    options.disableMutationObserver = true;
+  }
+
   /**
    * Observe [aos] elements
    * If something is loaded by AJAX
    * it'll refresh plugin automatically
    */
   if (!options.disableMutationObserver) {
-    observe('[data-aos]', refreshHard);
+    observer.ready('[data-aos]', refreshHard);
   }
 
   /**

src/js/libs/observer.js

@@ -20,23 +20,6 @@ function containsAOSNode(nodes) {
   return false;
 }
 
-function ready(selector, fn) {
-  const doc = window.document;
-  const MutationObserver =
-    window.MutationObserver ||
-    window.WebKitMutationObserver ||
-    window.MozMutationObserver;
-
-  const observer = new MutationObserver(check);
-  callback = fn;
-
-  observer.observe(doc.documentElement, {
-    childList: true,
-    subtree: true,
-    removedNodes: true
-  });
-}
-
 function check(mutations) {
   if (!mutations) return;
 
@@ -51,4 +34,30 @@ function check(mutations) {
   });
 }
 
-export default ready;
+function getMutationObserver() {
+  return (
+    window.MutationObserver ||
+    window.WebKitMutationObserver ||
+    window.MozMutationObserver
+  );
+}
+
+function isSupported() {
+  return !!getMutationObserver();
+}
+
+function ready(selector, fn) {
+  const doc = window.document;
+  const MutationObserver = getMutationObserver();
+
+  const observer = new MutationObserver(check);
+  callback = fn;
+
+  observer.observe(doc.documentElement, {
+    childList: true,
+    subtree: true,
+    removedNodes: true
+  });
+}
+
+export default { isSupported, ready };