An interview test: Convert a string "1234" into an integer 1234 without using parseInt or Number

converter.js

function converter(st){

  var arrSt = st.split(''),
      arrInt = [];

  for (var i = 0; i < arrSt.length; i++){
    arrInt.push(arrSt[i].charCodeAt() - 48);
  }

  // loop over arry again
  var counter = 0, num;

  for (var j = 0; j < arrInt.length; j++ ){

    num = Math.pow(10, arrInt.length - j - 1 );

    counter += arrInt[j] * num;
  }

  return counter;
}

This is just stupid