title: Create Phone Number coding challenge
body: <p>Can someone explain me what wrong with my code below? </p>
  
  <p><strong>Write a function that accepts an array of 10 integers (between 0 and 9), that returns a string of those numbers in the form of a phone number.
  Example:
  createPhoneNumber([1, 2, 3, 4, 5, 6, 7, 8, 9, 0]) // => returns "(123) 456-7890"
  The returned format must be correct in order to complete this challenge.
  Don't forget the space after the closing parentheses!</strong></p>
  
  <pre><code>function createPhoneNumber(numbers){
      let firstpart = ""
      let secondpart = ""
      let thirdpart = ""
      for(var i=0;i&lt;numbers.length;i++){
        if(i&lt;3){
          firstpart.concat(numbers[i].toString())
        } else if(3&lt;i&lt;6){
          secondpart.concat(numbers[i].toString())
        } else if(i&gt;=6){
          thirdpart.concat(numbers[i].toString())
        }
      }
      return `(${firstpart} ${secondpart}-${thirdpart}`
  }
  
  createPhoneNumber([1, 2, 3, 4, 5, 6, 7, 8, 9, 0])
  </code></pre>