How to search text and highlight the text that matches in a webpage.

var n   = 0;
function Findstring(searchstring) {
  
    if (document.all) {
    txt = window.document.body.createTextRange();//create a text range i.e all  text in webpage 
    for (i = 0; i <= n && (found = txt.findText(searchstring)) != false; i++) {
      txt.moveStart("character", 1);//move to next
      txt.moveEnd("textedit");//move to end
    }
    if (found) {
      txt.moveStart("character", -1);
      txt.findText(searchstring);
      txt.select();//hightlight the text
      txt.scrollIntoView();
      n++;
    }
    else {
        if (n > 0) {
            n = 0;
            Findstring(searchstring);
        }
        else {
            alert("Sorry, we couldn't find.Try again");
        }
   }
  }
  return false;
}