JS Функции. Калькулятор

Курсы Функции
1 
  let calculate = function(firstNumber,secondNumber,operator){
      let result;
      if(operator==='+'){
        result = Number(firstNumber)+Number(secondNumber);
      }
      if(operator==='-'){
        result = Number(firstNumber)-Number(secondNumber);
      }
      if(operator==='*'){
        result = Number(firstNumber)*Number(secondNumber);
      }
      if(operator==='/'){
        result = Number(firstNumber)/Number(secondNumber);
      }
      return result;
    }
2

Тоже самое, только немного по короче.

let calculate = function(firstNumber, secondNumber, operator){
  
  firstNumber = Number(firstNumber);
  secondNumber = Number(secondNumber);
  
  if(operator === '+'){
    return firstNumber + secondNumber; 
  }
  
   if(operator === '-'){
    return firstNumber - secondNumber; 
  }
  
  if(operator === '*'){
    return firstNumber * secondNumber; 
  }
  
   if(operator === '/'){
    return firstNumber / secondNumber; 
  }
  
}
3 
let calculate = function (firstNumber, secondNumber, operator) {
  if (operator === '+') {
    return Number(firstNumber) + Number(secondNumber)
    } else if (operator === '-') {
      return firstNumber - secondNumber
      } else if (operator === '*') {
       return firstNumber * secondNumber
        } else if (operator === '/') {
         return firstNumber / secondNumber
          }

  }