向上取整
var a = 23.2325236
var abc = Math.ceil(a); //注意:Math.ceil(a)不要單獨寫一行,否則向上取整失敗
abc = 24;
向下取整
var a = 23.2325236
var abc = Math.floor(a)//注意: Math.floor(a) 不要單獨寫一行,否則向下取整失敗
abc = 23;
四舍五入
Math.round(7/2);
