jQuery Animation Using Relative Values & Predefined Values

This method can also define relative values (the value is close to the element's current value). This is accomplished by appending += or -= to the value:

$("button").click(function(){
  $("div").animate({
    left: '250px',
    height: '+=150px',
    width: '+=150px'
  });
}); 

You can even specify the animation value for a property as "display," "hide," or "toggle":

$("button").click(function(){
  $("div").animate({
    height: 'toggle'
  });
});