JS: Prototype inheritance in Javascript

This post will discuss exclusively about Javascript’s prototype inheritance. Many JS frameworks leverage on prototype inheritance to add that extra bit black-magic in their tool.

Constructor

Any function call that is preceded by the new keyword acts as a constructor.

Prototypes

Object oriented-ness in Javascript is achieved by using prototype inheritance and late binding of this.

This

this can be bound in five different ways,

• Global scope, here this refers to the global object and any side affects on this object will affect global namespace and name-resolution.
• Function scope, inside functions this will again refer to global object.
• Constructor scope, functions when called with new prefix - will instantiate a new instance of object and this will be bound to that object-instance.
• Method scope, are functions bound to object-instances. this will always refer to the object-instance.
• Explicit setting, using apply and call methods from Function.prototype.

In case of setTimeout and setInterval timeout-handlers, this when used inside the handler function will refer to global object.