prototype methods

[DarkPark]

Is there a reason why some of your methods in prototype and some not?

[taylorhakes]

Yes, prototype methods are visible to the outside world, essentially public. It is common pattern to put private methods on prototype, but prefix with an underscore. i.e. Promise.prototype._privateFunc.

Since this library is a polyfill, I tried to make it as close to the built-in Promise as possible. The built-in Promise doesn't expose any underscore methods.

You can make true private methods using a closure and calling it like fn.apply(this, args). You still get the same performance benefits as the prototype methods, but the functions are not exposed to the outside world on the prototype. Does that make sense?

[DarkPark]

thank you for detailed explanation
I haven't check the native Prototype global object to see the same public methods
so now it's clear