code: function detectZoomRanges(zooms) {
      var ranges = [];
      var currentRange = [];
      for (var i = 0, z = zooms[0]; i <= zooms.length; i++, z = zooms[i]) {
          if (currentRange.length < 2) {
              currentRange.push(z);
              continue;
          }
          if (currentRange.length === 2) {
              if (z === currentRange[1] + 1) {
                  currentRange[1] = z;
              } else {
                  ranges.push(currentRange);
                  currentRange = [];
              }
          }
      }
      if (currentRange.length > 0) {
          ranges.push(currentRange);
      }
      return ranges;
  }
docs: Find zoom ranges in a set of zooms