The different components that are required in the functional model is :

First-class functions :

Fuctions that are first class will have some objects whose properties and methods are given by using the methods like length() and call(). These methods can be given different varibles and passed by an argumnent.

Nested functions :

These are the functions that are used in another function. It is created each time the outer function is invoked. If a function is used inside another then any constants, local variables and argument values, become part of the function object.

Closures :

JavaScript allows the function to be created with nested functionality. It usually try to find the combination of code that can be used to execute the application.