JAVASCRIPT

polymorphism javascript

//The fancy word for the ability of multiple object types to 
//implement the same functionality is polymorphism -MDN

polymorphism js

Perhaps in JavaScript, it is a bit more difficult to see the effects of polymorphism because the more classical types of polymorphism are more evident in static type systems, whereas JavaScript has a dynamic type system.

So, for instance, there is no method or function overloading or automatic type coercions at compile time in JavaScript. In a dynamic language, we take most of these things for granted. Neither we need something like parametric polymorphism in JavaScript due to the dynamic nature of the language.

Still, JavaScript has a form of type inheritance that emulates the same ideas of subtype polymorphism (classified as inclusion polymorphism by Cardelli above) in a similar way to what we typically do in other object-oriented programing languages like Java or C# (as explained in another answer I shared above).

Another form of polymorphism very typical in dynamic languages is called duck typing.

It is a mistake to believe that polymorphism is only related to object-oriented programming. Other programming models (functional, procedural, logic, etc.) offer different forms of polymorphism in their type systems, probably in a way a bit unfamiliar to those only used to OOP.