johnDebounce.js

function debounce(callback, wait, immediate) {
  var timeout;
  return function() {
    var context = this;
    var args = arguments;
    var delayedFire = function() {
      timeout = null;
      if (!immediate) callback.apply(context, args);
    };
    clearTimeout(timeout);
    timeout = setTimeout(delayedFire, wait);
    if (immediate && !timeout) callback.apply(context, args);
  }
}