expandrange.js

// Expand input of comma separated positive integers including ranges, into flat list of numbers.

var isValidRange = function(str, delimiter, rangeDelimiter) {
  return new RegExp('^[0-9]+(?:' + rangeDelimiter + '[0-9]+)?(?:' + delimiter+ '[0-9]+(?:' + rangeDelimiter + '[0-9]+)?)*$', 'i').test(str);
}
var addRange = function(low,high, result) {
  var i;
  for (i = low; i <= high; i++) result.push(i);
  return result;
}

var expandRange = function(str, delimiter, rangeDelimiter) {
  var regexp = new RegExp('([0-9]+)(?:' + rangeDelimiter + '([0-9]+))?(?:' + delimiter + '|$)', 'g'),
  segments = regexp.exec(str),
  result = [], i;

  while (segments) {
    for (i = 0; i < segments.length; i++) {
      if (segments[2] === undefined) result.push(parseInt(segments[1]));
      else result = addRange(parseInt(segments[1]), parseInt(segments[2]), result);
    }
    segments = regexp.exec(str);
  }
  return Array.from(new Set(result)).sort(function(a, b){return a - b});
}

document.querySelector('button').addEventListener('click', function(e) {
  var delimiter = ',', rangeDelimiter = '-', result = '';
  var value = (delimiter === ' ') ? this.value.replace(/ +/g, " ") : this.value.replace(/ /g, "");
  if (isValidRange(value, delimiter, rangeDelimiter)) result = 'Expanded: ' + expandRange(value, delimiter, rangeDelimiter).toString();
  else result = 'Error: Invalid input';
  document.querySelector('#output').innerText = result;

}.bind(document.querySelector('#number')));