text: function encode(input) {
      var encoding = [];
      var prev, count, i;
      for (count = 1, prev = input[0], i = 1; i < input.length; i++) {
          if (input[i] != prev) {
              encoding.push([count, prev]);
              count = 1;
              prev = input[i];
          }
          else
              count ++;
      }
      encoding.push([count, prev]);
      return encoding;
  }
  