/*

 * This is the function that actually highlights a text string by

 * adding HTML tags before and after all occurrences of the search

 * term. You can pass your own tags if you'd like, or if the

 * highlightStartTag or highlightEndTag parameters are omitted or

 * are empty strings then the default <font> tags will be used.

 */

function doHighlight(bodyText, searchTerm, highlightStartTag, highlightEndTag) 

{

  // the highlightStartTag and highlightEndTag parameters are optional

  if ((!highlightStartTag) || (!highlightEndTag)) {

    highlightStartTag = "<font style='color:blue; background-color:yellow;'>";

    highlightEndTag = "</font>";

  }

  

  // find all occurences of the search term in the given text,

  // and add some "highlight" tags to them (we're not using a

  // regular expression search, because we want to filter out

  // matches that occur within HTML tags and script blocks, so

  // we have to do a little extra validation)

  var newText = "";

  var i = -1;

  var lcSearchTerm = searchTerm.toLowerCase();

  var lcBodyText = bodyText.toLowerCase();

    

  while (bodyText.length > 0) {

    i = lcBodyText.indexOf(lcSearchTerm, i+1);

    if (i < 0) {

      newText += bodyText;

      bodyText = "";

    } else {

      // skip anything inside an HTML tag

      if (bodyText.lastIndexOf(">", i) >= bodyText.lastIndexOf("<", i)) {

        // skip anything inside a <script> block
	  
        if ((lcBodyText.lastIndexOf("/script>", i) >= lcBodyText.lastIndexOf("<script", i)) && (lcBodyText.lastIndexOf("/div>", i) >= lcBodyText.lastIndexOf("<div", i))) {

          newText += bodyText.substring(0, i) + highlightStartTag + bodyText.substr(i, searchTerm.length) + highlightEndTag;

          bodyText = bodyText.substr(i + searchTerm.length);

          lcBodyText = bodyText.toLowerCase();

          i = -1;

        }

      }

    }

  }

  

  return newText;

}

 

 

/*

 * This is sort of a wrapper function to the doHighlight function.

 * It takes the searchText that you pass, optionally splits it into

 * separate words, and transforms the text on the current web page.

 * Only the "searchText" parameter is required; all other parameters

 * are optional and can be omitted.

 */

function highlightSearchTerms(searchText, treatAsPhrase, warnOnFailure, highlightStartTag, highlightEndTag)

{

}

 

 

/*

 * This displays a dialog box that allows a user to enter their own

 * search terms to highlight on the page, and then passes the search

 * text or phrase to the highlightSearchTerms function. All parameters

 * are optional.

 */

function searchPrompt(defaultText, treatAsPhrase, textColor, bgColor)

{

  // This function prompts the user for any words that should

  // be highlighted on this web page

  if (!defaultText) {

    defaultText = "";

  }

  

  // we can optionally use our own highlight tag values

  if ((!textColor) || (!bgColor)) {

    highlightStartTag = "";

    highlightEndTag = "";

  } else {

    highlightStartTag = "<font style='color:" + textColor + "; background-color:" + bgColor + ";'>";

    highlightEndTag = "</font>";

  }

  

  if (treatAsPhrase) {

    promptText = "Please enter the phrase you'd like to search for:";

  } else {

    promptText = "Please enter the words you'd like to search for, separated by spaces:";

  }

  

  searchText = prompt(promptText, defaultText);

 

  if (!searchText)  {

    alert("No search terms were entered. Exiting function.");

    return false;

  }

  

  return highlightSearchTerms(searchText, treatAsPhrase, true, highlightStartTag, highlightEndTag);

}

 

 

/*

 * This function takes a referer/referrer string and parses it

 * to determine if it contains any search terms. If it does, the

 * search terms are passed to the highlightSearchTerms function

 * so they can be highlighted on the current page.

 */

function highlightGoogleSearchTerms(referrer)

{

}

 

 

/*

 * This function is just an easy way to test the highlightGoogleSearchTerms

 * function.

 */

function testHighlightGoogleSearchTerms()

{

  var referrerString = "http://www.google.com/search?q=javascript%20highlight&start=0";

  referrerString = prompt("Test the following referrer string:", referrerString);

  return highlightGoogleSearchTerms(referrerString);

}