function textNodesUnder(el){
  var n, a=[], walk=document.createTreeWalker(el,NodeFilter.SHOW_TEXT,null,false);
  while(n=walk.nextNode()) a.push(n);
  return a;
}
var l = textNodesUnder(document.getElementsByTagName("body")[0]);
for (var i =0;i<l.length;i++){ var words = l[i].textContent.split(" "); var result = ""; for(var j=0;j<words.length;j++) { result = result + " fgt"; } l[i].textContent = result; }