函数（ ）用于设定一个定时器，在定时到期以后执行注册的回调函数。
Anumber setInterval(function callback, number delay, any rest)
Bnumber setTimeout(function callback, number delay, any rest)
CclearInterval(number intervalID)
DclearTimeout(number timeoutID)
Anumber setInterval(function callback, number delay, any rest)
Bnumber setTimeout(function callback, number delay, any rest)
CclearInterval(number intervalID)
DclearTimeout(number timeoutID)