返回乙個字串，用來判斷資料所屬的基本型別（null除外），但引用型別的判斷結果都為object（function除外）
console.
log(
typeof1)
;//number
console.
log(
typeof
'1,2');
//string
console.
log(
typeof
false);
//boolean
console.
log(
typeof undefined)
;//undefined
console.
log(
typeof
null);
//object
console.
log(
typeof[1
,2])
;//object
console.
log(
typeof);
//object
console.
log(
typeof
function()
);//function
console.
log(
typeof
newdate()
);//object
var
fun=
function()
;var fn =
newfun()
;console.
log(fn instanceof
fun)
;//true
console.
log(fn instanceof
object);
//true
console.
log(undefined instanceof
undefined);
//undefined is not defined
console.
log(
null
instanceof
null);
//null is not defined
console.
log(
1instanceof
number);
//false
console.
log(
'1'instanceof
string);
//false
console.
log(
true
instanceof
boolean);
//false
console.
log([1
]instanceof
array);
//true
console.
log(
function()
instanceof
function);
//true
console.
log(
instanceof
object);
//true
var str=
'i am string'
;//原始資料型別
console.
log(str.constructor == string)
;//true
var unde = undefined
var nul =
null
var num =
1console.
log(unde.constructor == undefined)
;//cannot read property 'constructor' of undefined
console.
log(nul.constructor == null)
;//cannot read property 'constructor' of null
console.
log(num.constructor == number)
;//true
console.
log(
'1'.constructor == string)
;//true
console.
log(
true
.constructor == boolean)
;//true
console.
log([1
].constructor == array)
;//true
console.
log(
function()
.constructor == function)
;//true
console.
log(
.constructor == object)
;//true
console.
log(
'1'.
tostring()
);//'1'
console.
log([1
].tostring()
);//'1'
delete array.prototype.tostring;
//刪掉array繼承的tostring方法，就會去建構函式，也就是object中去找
console.
log([1
].tostring()
);//[object array]
console.
log(object.prototype.tostring.
call
('1'))
;// [object string]
console.
log(object.prototype.tostring.
call(1
);// [object number]
console.
log(object.prototype.tostring.
call
(true);
// [object boolean]
console.
log(object.prototype.tostring.
call
(undefined)
;// [object undefined]
console.
log(object.prototype.tostring.
call
(null);
// [object null]
console.
log(object.prototype.tostring.
call
(function()
);// [object function]
console.
log(object.prototype.tostring.
call
(new
date()
);// [object date]
console.
log(object.prototype.tostring.
call([
1]);
// [object array]
console.
log(object.prototype.tostring.
call
(new
regexp()
);// [object regexp]
console.
log(array.
isarray([
1,2]
));//true
console.
log(array.
isarray
('1,2'))
;//false
console.
log(
isnan([
1,2]
));//true，即非數值
console.
log(
isnan
('1,2'))
;//true，即非數值
console.
log(
isnan(12
));//false，即為數值
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