code: function cmpVersion(a, b) {
      "use strict";
      var i, cmp, len, re = /(\.0)+[^\.]*$/;
      a = versionToString(a);
      b = versionToString(b);
      a = (a + '').replace(re, '').split('.');
      b = (b + '').replace(re, '').split('.');
      len = Math.min(a.length, b.length);
      for (i = 0; i < len; i++) {
          cmp = parseInt(a[i], 10) - parseInt(b[i], 10);
          if (cmp !== 0) {
              return cmp;
          }
      }
      return a.length - b.length;
  }
docs: Compare two version numbers represented as strings.
  
  @param  String  a  Version a
  @param  String  b  Version b
  @return Number