javascript平滑动画从X,Y到X1,Y1

function translate( elem,x,y ) {
    var left = parseInt( css( elem,'left' ),10 ),top = parseInt( css( elem,'top' ),dx = left - x,dy = top - y,i = 1,count = 20,delay = 20;

    function loop() {
        if ( i >= count ) { return; }
        i += 1;
        elem.style.left = ( left - ( dx * i / count ) ).toFixed( 0 ) + 'px';
        elem.style.top = ( top - ( dy * i / count ) ).toFixed( 0 ) + 'px';
        setTimeout( loop,delay );
    }

    loop();
}

function css( element,property ) {
    return window.getComputedStyle( element,null ).getPropertyValue( property );
}

现场演示：http://jsfiddle.net/qEVVT/1/