funnyURL.js

function funnyURL(word, interval, prevID) {
  prevID = prevID ? prevID : this.prevID; // assume that undefined is OK
  clearInterval(prevID);   
  
  var i = 0, ID;
  ID = setInterval(function() {
    history.replaceState(null, '', word.slice(0,i+1));
    i = i+1;
    if (i >= word.length) clearInterval(ID);
  }, interval);

  return this.prevID = ID;
}