js的向上取整(Math.ceil)向下取整(Math.floor)四舍五入(Math.round)

<script language="javascript">
Math.floor(5.55) //向下取整 结果为5
Math.floor(5.99) //向下取整 结果为5
Math.ceil(5.21) //向上取整，结果为6
Math.ceil(5.88) //向上取整，结果为6
Math.round(5.78) //四舍五入 结果为6
Math.round(5.33) //结果为5
</script>