function doMove ( obj, attr, dir, target, endFn ) {    dir = parseInt(getStyle( obj, attr )) < target ? dir : -dir;    clearInterval( obj.timer );    obj.timer = setInterval(function () {        var speed = parseInt(getStyle( obj, attr )) + dir;            // 步长        if ( speed > target && dir > 0 ||  speed < target && dir < 0  ) {            speed = target;        }        obj.style[attr] = speed + 'px';        if ( speed == target ) {            clearInterval( obj.timer );            /*            if ( endFn ) {                endFn();            }            */            endFn && endFn();        }    }, 30);}function getStyle ( obj, attr ) { return obj.currentStyle?obj.currentStyle[attr] : getComputedStyle( obj )[attr]; }