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Function

Function Types​

//in functions, we can specify parameter variable to accept only certain types
let sayHi = (name:string) => {
	return 'Hello ' + name;
}

let mysquare = (num:number) => {
	return num*num;
}

Multiple parameters​

const doSomething = (lastname:string, firstname:string, age:number) => {
  return "hello " + lastname + firstname + ", you are " + age + " years old";	
}

Default Value​

const sayHi = (name:string='stranger') => {
  return "hello! " + name;	
}

Return type​

const addNums = (x:number) :boolean => {
  return Math.sign(x);;	
}

Void type​

//Should not return anything, if we return aything typescript will complain
const addNums = (x:number) :void => {
  console.log(x);	
}

Never type​

//this function does not have a chance of returning anything
const gameLoop=():never => {
  while(true){console.log('keep playing');}
}