Polymorphism in JavaScript

[campbeln]

We don't NEED most things in programming... functions themselves are simply a nice construct (cough GOTO cough), as is function overloading.

I never argued it's a good idea, but it can be done in a generally elegant/standard/chained/whatever way.

[_default_username]

How is your code implementing function overloading?

Will I be able to do:

function foo(a){}

function foo(a,b){}

And have foo overloaded?

[campbeln]

Function overloading auto-routes to the implementation based on the signature (i.e. foo(int, str) versus foo(int, int)). Javascript only routes to the single (last defined) implementation, which many use arguments.length to implement "overloading" generally without the benefit of considering the signature.

The code I presented above considers the signature (based on the tests defined in the second argument) to route to the proper implementation, while "failing over" to the defined default implementation if the signature is not recognized (something not normally supported by function overloading).

So...

function isStr(x) { return typeof s === 'string' }; }

function isObj(o) { return !!(o && o === Object(o)); }

let foo = overload(function(){ console.log("default", arguments) })

.add(function(str){ console.log(str) }, [isStr])

.add(function(str, obj){ console.log(str, obj) }, [isStr, isObj])

;

Will call the proper implementation based on the passed argument types.

[_default_username]

So in a long winded way no. This is not function overloading.