fix(zone.js): zone.js toString patch should check typeof Promise is function (#38350)

rifler · mhevery · commit 18e474f522ed · 2020-08-25T09:51:50.000-07:00
Close #38361 zone.js monkey patch toString, and check the instance is `Promise` or not by using `instanceof Promise`, sometimes when Promise is not available, the `instanceof` operation fails and throw `TypeError: Right-hand side of 'instanceof' is not an object` this PR check `typeof Promise` equals to function or not to prevent the error. PR Close #38350
diff --git a/packages/zone.js/lib/common/to-string.ts b/packages/zone.js/lib/common/to-string.ts
@@ -49,9 +49,10 @@ Zone.__load_patch('toString', (global: any) => {
   const originalObjectToString = Object.prototype.toString;
   const PROMISE_OBJECT_TO_STRING = '[object Promise]';
   Object.prototype.toString = function() {
-    if (this instanceof Promise) {
+    if (typeof Promise === 'function' && this instanceof Promise) {
       return PROMISE_OBJECT_TO_STRING;
     }
+
     return originalObjectToString.call(this);
   };
 });
diff --git a/packages/zone.js/test/common/toString.spec.ts b/packages/zone.js/test/common/toString.spec.ts
@@ -18,6 +18,18 @@ describe('global function patch', () => {
           .toEqual(Function.prototype.toString.call(g[zoneSymbol('setTimeout')]));
     });
 
+    it('should not throw error if Promise is not a function', () => {
+      const P = g.Promise;
+      try {
+        g.Promise = undefined;
+        expect(() => {
+          const a = {}.toString();
+        }).not.toThrow();
+      } finally {
+        g.Promise = P;
+      }
+    });
+
     it('MutationObserver toString should be the same with native version',
        ifEnvSupports('MutationObserver', () => {
          const nativeMutationObserver = g[zoneSymbol('MutationObserver')];
