code: function compareSpecificity(first, second) {
      for (var i = 0; i < first.length; i++) {
          var a = first[i];
          var b = second[i];
  
          if (a === b) {
              continue;
          }
  
          return a - b;
      }
  
      return 0;
  }
docs: 优先级比较算法
  @see     getSpecificity
  @return  {Number}