code: public Object pop() {
          //Object obj = jsObject.getSlot(jsLen - 1);
          Object obj = invokeJavascript("pop");
          if (obj instanceof JSObject && content.containsKey((JSObject) obj)) {
              return (JavascriptObject) content.get((JSObject) obj);
          }
          return obj;
      }
docs: pop() 	Removes the last element of an array, and returns that element