Function

Param Syntax

export function twoFer(param: int): string {
	...
}

• (): string is called a return type

  • It's a type of the value that is returned from a function

• (param: int) represents the parameters for the function

  • Parameters need their own typing

• export allows the test to import the function and call it

// Optional Parameter `y`
function newFunc(x: number, y?: number) {
  ...
}

// Default Parameter
function newFunc(name: string = "you"){
  ...
}

function applyDiscount(price: number, discount: number = 0.05): number {
    return price * (1 - discount);
}

console.log(applyDiscount(100)); // 95

Return Types

// void return type
function messageLogger(message: string): void {
  console.log(message);
}

// primitive return type
function addNumbers(a: number, b: number): number {
  return a + b;
}

Function Expression

Function Expression with number return type

const addNumbers = (a: number, b: number): number => a + b;