This can be the case for big or difficult to implement functionality like async/await. But for smaller functions like isArray, isObject and leftpad this should

This can be the case for big or difficult to implement functionality like async/await. But for smaller functions like isArray, isObject and leftpad this should not be the case. C++ has a lot of different standards, compilers and implementations. There are differences in vc++ and gcc that can prevent compilation without flags or custom implementations. But I am sure that simple functions like printf or strcpy behave same across implementations. Even in Java you have Oracle JVM and android's custom dalvik/ART. But the standard Java functions still work the same. Same with .net/mono.