code: function highlight() {
      $('pre code').each(function (i, block) {
        hljs.highlightBlock(block);
      });
      $('pre code[highlight-lines]').each(function (i, block) {
        if (block.innerHTML === "") return;
        var lines = block.innerHTML.split('\n');
  
        queryString = block.getAttribute('highlight-lines');
        if (!queryString) return;
  
        var ranges = queryString.split(',');
        for (var j = 0, range; range = ranges[j++];) {
          var found = range.match(/^(\d+)\-(\d+)?$/);
          if (found) {
            // consider region as `{startlinenumber}-{endlinenumber}`, in which {endlinenumber} is optional
            var start = +found[1];
            var end = +found[2];
            if (isNaN(end) || end > lines.length) {
              end = lines.length;
            }
          } else {
            // consider region as a sigine line number
            if (isNaN(range)) continue;
            var start = +range;
            var end = start;
          }
          if (start <= 0 || end <= 0 || start > end || start > lines.length) {
            // skip current region if invalid
            continue;
          }
          lines[start - 1] = '<span class="line-highlight">' + lines[start - 1];
          lines[end - 1] = lines[end - 1] + '</span>';
        }
  
        block.innerHTML = lines.join('\n');
      });
    }
docs: Enable highlight.js