Display latest value of a variable instead of flooding your console with log entries with this handy script. Call dbgWatch with 2 parameters: variable name, variable value, and it places it in a fixed-position div on the page. You can move the div around as needed.

dbgWatch.js

/***************************************************
 * Debugging
 ***************************************************/
(function() {
  var body     = document.getElementsByTagName('body')[0],
      divWatch = document.createElement('div');
      cssText = "font-family: 'Lucida Console', monospace;" +
        "font-size: 12px;" +
        "line-height: 1em;" +
        "white-space: nowrap;" +
        "text-align: left;" +
        "padding: 10px;" +
        "background: white;" +
        "color: black;" +
        "position: fixed;" +
        "top: 90px;" +
        "left: 90px;" +
        "box-shadow: 0 0 10px rgba(0,0,0,0.7);" +
        "cursor: move;" +
        "user-select: none;" +
        "-webkit-user-select: none;" +
        "-moz-user-select: none;" +
        "-ms-user-select: none;" +
        "z-index: 9999;";

  divWatch.id = 'debug-watch';
  divWatch.style.cssText = cssText;
  body.appendChild(divWatch);

  divWatch.addEventListener('mousedown', addMoveEvent);
  divWatch.addEventListener('mouseup', removeMoveEvent);

  function addMoveEvent() {
    body.addEventListener('mousemove', moveDiv);
  }

  function removeMoveEvent() {
    body.removeEventListener('mousemove', moveDiv);
  }

  function moveDiv(e) {
    divWatch.style.top = e.y + 'px';
    divWatch.style.left = e.x + 'px';
  }

  window.dbgWatch = function(name, value) {
    var watcharea = document.querySelector('#debug-watch'),
        var_name = name.replace('.','-'),
        text = name + ': ' + value;

    try {
      var elWatch = watcharea.querySelector('#var-' + name);

      if (elWatch) {
        elWatch.textContent = text;
      }
      else {
        // Create new var space on the #debug-watch output
        var newElWatch = document.createElement('div');
        newElWatch.id = 'var-' + name;
        newElWatch.textContent = text;
        watcharea.appendChild(newElWatch);
      }
    } catch(e) {}
  };
})();