Podstawowy kalkulator dla dwóch liczb

const calculator = (a, b, operator) => {
  let resultNum = 0
    switch (operator) {
      case "add":
        resultNum = a + b;
        break;
      case "subtract":
        resultNum = a - b;
        break;
      case "multiply":
        resultNum = a * b;
        break;
      case "divide":
        resultNum = a / b;
        break;
      default:
        resultNum = 0;
    }
  return resultNum
}

// With love @kouqhar
kouqhar