Functions

JavaScript, which follows the ES5 specs, does not support classes and modules. However, we tried to scope variables and modularity using functional programming in JavaScript. Functions are the building blocks of an application in JavaScript.

Though TypeScript supports classes and modules, functions play a key role in defining a specific logic. We can define both named functions and anonymous functions in JavaScript as follows:

//Named function 
function multiply(a, b) { 
    return a * b; 
} 
 
//Anonymous function 
var result = function(a, b) { return a * b; }; 

In TypeScript, we define functions with the type of the parameters and the return type using function arrow notation, which is also supported in ES6, as follows:

var multiply:(a: number, b: number) => number = 
          function(a: number, b: number): number { return a * b; };