makeshift semantic version comparison

semver.js

// makeshift semantic version comparisons
// standard compareFunction
// Checks if semver a is greater than semver b
function gtSemver(a, b) {
  // validate
  if (!a && !b) { return 0; }
  if (!a) { return -1; }
  if (!b) { return 1; }
  if (!_.isString(a) || !_.isString(b)) {
    throw new Error('Semver not valid "' + a + '", "' + b + '"');
  }
  // helpers
  var reg = /(\d+)\.(\d+)\.(\d+)(-?.*)/;
  var toInt = function(num) { return parseInt(num, 10); };
  var cmp = function(a, b) {
    if (a < b) { return -1; }
    if (a > b) { return 1; }
    return 0;
  };
  
  // break the semver into parts
  a = a.match(reg);
  b = b.match(reg);
  // we can only compare numbers (per semver)
  a = a.slice(1, 4);
  b = b.slice(1, 4);
  // to numbers!
  a = a.map(toInt);
  b = b.map(toInt);
  
  // compare in order
  return cmp(a[0], b[0]) || cmp(a[1], b[1]) || cmp(a[2], b[2]);
}

Codepen: http://codepen.io/anon/pen/XJaGeP?editors=101