详解ECMAScript typeof用法

> var b
undefined
> typeof(b)
'undefined'
> typeof e
'undefined'
>

> var a = new  ()
undefined
> typeof a
' '
> var b = new String("str")
undefined
> typeof b
' '
> var c = new Boolean(false)
undefined
> typeof c
' '
>
> var d = []
undefined
> typeof d
' '
>
> var e = {}
undefined
> typeof e
' '
>

> var a = 98
undefined
> typeof a
'number'
> var b = 'aaa'
undefined
> typeof b
'string'
> var c = true
undefined
> typeof c
'boolean'
>