Caesar Cipher in Javascript

I have tried to make it simple and I earned FREE PIZZA!. Check my solution for this.

    function rot13(str) {
    
    var alphabets =['A','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P','Q','R','S','T','U','V','W','X','Y','Z'," ", "-", "_", ".", "&","?", "!", "@", "#", "/"];
    
    var alphabets13 = ['N','O','P','Q','R','S','T','U','V','W','X','Y','Z','A','B','C','D','E','F','G','H','I','J','K','L','M', " ", "-", "_", ".", "&","?", "!", "@", "#", "/"];
    
    var resultStr = [];
    for(let i=0; i<str.length; i++){
        for(let j =0; j<alphabets.length; j++){
            if(str[i] === alphabets[j]){
            resultStr.push(alphabets13[j]);
            }
        }
    }
    return resultStr.join("");
  };

  rot13("SERR CVMMN!");