The sum of a range

/* 
  My answer for exercise 'The sum of a range'
  in Eloquent JavaScript Second Edition
  Chapter 4 Data Structures: Objects and Arrays 
*/

function range(first, second, third) {
  var array = [];
  if (first < second) {
  while (first <= second ) {
   array.push(first++);
    
  }
  
  } else {
    while (first >= second) {
      array.push(first--);
      
    }
    
  }
  return array;
}

function sum(array) {
  var output = 0;
  for(var i = 0; i < array.length; i++) {
    output += array[i];
    
  }
  return output;
}