tween.js

var Tween = (function () {

  var animations = {}, nanim = 0;
  
  var Tween = {};
  
  Tween.step = function () {
    var d = new Date();
    var thisTick = d.getTime();
    
    for (var a in animations) {
      var anim = animations[a];
      if (thisTick > (anim.start + anim.end)) {
        delete animations[a];
        anim.assign(anim.to);
        if (anim.callback !== undefined) {
          anim.callback();
        }
        nanim--;
      } else {
        anim.assign(Tween[anim.interpolation](anim.from, anim.to, (thisTick - anim.start) / anim.end));
      }
    }
    
    if (nanim > 0) {
      setTimeout(Tween.step, 20);
    }
  };
  
  Tween.anim = function (identifier, object, variable, from, to, time, method, callback) {
    var d = new Date();
    var thisTick = d.getTime();
    
    var t = {
      assign: typeof object[variable] === "function" ?
        function (value) {
          object[variable](value);
        } :
        function (value) {
          object[variable] = value;
        },
      start: thisTick,
      end: time,
      from: from,
      to: to,
      interpolation: method === undefined ? "linear" : method,
      callback: callback
    };
    
    if (animations[identifier] === undefined) {
      nanim++;
    }
    animations[identifier] = t;
    
    if (nanim === 1) {
      Tween.step();
    }
  };
  
  Tween.linear = function (from, to, t) {
    return (t * (to-from)) + from;
  };
  
  Tween.quadratic = function (from, to, t) {
    return (t*t * (to-from)) + from;
  };
  
  Tween.invQuadratic = function (from, to, t) {
    var u = 1-t;
    return Tween.quadratic(to, from, u);
  }
  
  return Tween;

}());

watch.js

var Watch = (function () {

  document.write('<div id="watchPanel">&nbsp;</div>');
  var watchDiv = document.getElementById("watchPanel"),
      watchObj = undefined,
      staticLink = false;
  
  (function watchLoop() {
    var html = "";
    if (watchObj === undefined) {
      html = "Watching Nothing.";
    } else {
      var watchVariable;
      if (staticLink) {
        watchVariable = eval(watchObj);
      } else {
        watchVariable = watchObj;
      }
      try {
        html = JSON.stringify(watchVariable);
      } catch (err) {
        html = "Sorry, I can't watch circular structures.";
      }
    }
    watchDiv.innerHTML = html;
    
    setTimeout(watchLoop, 20);
  }());
  
  return function (object) {
    staticLink = (typeof object !== "object");
    watchObj = object;
  };

}());