Sum the numbers in an array satisfying the given condition (even or odd)

Conditional Sum

function conditionalSum(data, cond){
  let arraySize = data.length;
  //special case
  if (arraySize === 0){
    return 0;
  }
  //determines which type of numbers need to be added (ie. odd or even)
  let rem;
  if (cond === 'even'){
    rem = 0;
  } else {
    rem = 1;
  }
  //adds the appropriate numbers
  let total = 0;
  for (i = 0; i < arraySize; i++){
    if (data[i] % 2 === rem){
      total += data[i];
    }
  }
  return total;
}