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Functions

Implicit Declaration -> Signature of this function would be

  • Input = Null
  • Output = void
const print = () => {
  console.log("Rishabh");
};

Return Type Defined -> Only boolean value has to be returned from this function. The number of input this function can take is 0.

const print = (): void => {
  console.log("Hello");
};

const returnTrue = (): boolean => {
  return true;
};

Input Parameters Defined -> This function can only have one argument and that can only be a number.

const alwaysEven = (num: number): number => {
  return number * 2;
};

Prefer using this style

Different ways for defining function signature

  1. function
function alwaysEven(num: number) {
  return num * 2;
}

function alwaysEven(num: number): number {
  return num * 2;
}
  1. function as variable
const alwaysEven = function (num: number) {
  return num * 2;
};

const alwaysEven = function (num: number): number {
  return num * 2;
};
  1. arrow functions
const alwaysEven = (num: number): number => {
  return num * 2;
};

const alwaysEven: (num: number) => number = (num) => {
  return num * 2;
};

Higher Order Functions

const display = (printFunction: (message: string) => void): void => {
  printFunction("Rishabh");
};

Functions signature can be defined using [[type]] or [[Interface]]