Un programa que presente un menú con: suma, resta, multiplicar, dividir y salir

Script
function add(a, b){
  return a + b;
}

function substract(a, b){
  return a - b;
}

function multiply(a, b){
  return a * b;
}

function divide(a, b){
  return a / b;
}

function choice(){
  var choice = prompt("What do you want to do? \n\n 1. Add \n\n 2. Substract \n\n 3. Multiply \n\n 4. Divide \n\n 5. Exit")
  var a = parseInt(prompt("Enter the first number"));
  var b = parseInt(prompt("Enter the second number"));
  if(choice === "1"){
    alert(add(a, b));
  }else if(choice === "2"){
    alert(substract(a, b));
  }else if(choice === "3"){
    alert(multiply(a, b));
  }else if(choice === "4"){
    alert(divide