Check if 'str' property already exist

Property should not be defined if already existing

Author: Wernfried

snippets/mongocompat/mongotypes.js

@@ -414,12 +414,14 @@ ObjectId.prototype.tojson = function() {
     return this.toString();
 };
 
-Object.defineProperty(ObjectId.prototype, 'str', {
-  enumerable: true,
-  get() {
-    return this.toHexString();
-  }
-});
+if (!ObjectId.prototype.hasOwnProperty('str')) {
+  Object.defineProperty(ObjectId.prototype, 'str', {
+    enumerable: true,
+    get() {
+      return this.toHexString();
+    }
+  });
+}
 
 ObjectId.prototype.valueOf = function() {
     return this.str;