看了這個就弄明白各種數據類型了

alert(typeof(1));//number
alert(typeof(NaN));//number
alert(typeof(Number.MIN_VALUE));//number
alert(typeof(Infinity));//number
alert(typeof("123"));//string
alert(typeof(true));//boolean
alert(typeof(window));//object
alert(typeof(document));//object
alert(typeof(null));//object
alert(typeof(eval));//function
alert(typeof(Date));//function
alert(typeof(sss));//undefined
alert(typeof(undefined));//undefined