Fix for the issue #20

Author: que-etc

src/index.js

@@ -1,10 +1,10 @@
 import ResizeObserverPolyfill from './ResizeObserver.js';
+import global from './shims/global.js';
 
 export default (() => {
     // Export existing implementation if available.
-    if (typeof ResizeObserver != 'undefined') {
-        // eslint-disable-next-line no-undef
-        return ResizeObserver;
+    if (typeof global.ResizeObserver != 'undefined') {
+        return global.ResizeObserver;
     }
 
     return ResizeObserverPolyfill;

src/shims/global.js

@@ -0,0 +1,16 @@
+export default (() => {
+    if (typeof global != 'undefined' && global.Math === Math) {
+        return global;
+    }
+
+    if (typeof self != 'undefined' && self.Math === Math) {
+        return self;
+    }
+
+    if (typeof window != 'undefined' && window.Math === Math) {
+        return window;
+    }
+
+    // eslint-disable-next-line no-new-func
+    return Function('return this')();
+})();

src/shims/requestAnimationFrame.js

@@ -1,3 +1,5 @@
+import global from './global.js';
+
 /**
  * A shim for the requestAnimationFrame which falls back to the setTimeout if
  * first one is not supported.
@@ -6,7 +8,10 @@
  */
 export default (() => {
     if (typeof requestAnimationFrame === 'function') {
-        return requestAnimationFrame;
+        // It's required to use a bounded function because IE sometimes throws
+        // an "Invalid calling object" error if rAF is invoked without the global
+        // object on the left hand side.
+        return requestAnimationFrame.bind(global);
     }
 
     return callback => setTimeout(() => callback(Date.now()), 1000 / 60);