gistfile1.js

  var highlightClass = 'hl'; 
  
  function createHighlights(text, regex, node,parentn) {
    if (regex.exec(text) != null) {
      parentn.insertBefore(document.createTextNode(RegExp.$1),node);
     
      highlightNode = document.createElement("span");
      highlightNode.className = highlightClass;
      highlightNode.appendChild(document.createTextNode(RegExp.$2)); 
      
      parentn.insertBefore(highlightNode,node);
      createHighlights(RegExp.$3, regex, node,parentn);
    } else {
      parentn.insertBefore(document.createTextNode(text),node);
    } 
  } 
  
  function highlightWord(node, word) {
    var wordRegex = new RegExp('(.*?)\\b(' + word + ')\\b(.*)', 'i'); 
    if (node.nodeType == 3 && wordRegex.test(node.nodeValue)) { // text node
        var parentn = node.parentNode; 
        createHighlights(node.nodeValue, wordRegex,node,parentn);
        parentn.removeChild(node);
    } else if (node.hasChildNodes()) {
      var childNodes = node.childNodes;
      for (var i=0; i<childNodes.length; ++i) {
        var next_node = childNodes[i];
          if (next_node.parentNode.className != highlightClass){
            highlightWord(next_node, word);
          }
      }
    }
  }