判斷資料型別 toString

每個物件都有乙個tostring()方法，當該物件被表示為乙個文字值時，或者乙個物件以預期的字串方式引用時自動呼叫。

預設情況下，tostring()方法被每個object物件繼承，如果該方法沒有在自定義物件中被覆蓋，tostring()返回'[object type]'，其中type是型別

const obj =

newobject()
;console.
log(obj.
tostring()
);// [object object]

/**

* @name 示例
* @description tostring 檢測物件型別
*/const tostring = object.prototype.tostring;
console.
log(tostring.
call
(new
date))
;// [object date]
console.
log(tostring.
call
(new
string))
;// [object string]
console.
log(tostring.
call
(math));
// [object math]
console.
log(tostring.
call
('***x'))
;// [object string]
console.
log(tostring.
call
(123))
;// [object number]
console.
log(tostring.
call([
]));
// [object array]
console.
log(tostring.
call()
);// [object object]
console.
log(tostring.
call
(undefined));
// [object undefined]
console.
log(tostring.
call
(null))
;// [object null]
console.
log(
'------');
console.
log(tostring.
(new
date))
;// [object date]
console.
log(tostring.
(new
string))
;// [object string]
console.
log(tostring.
(math));
// [object math]
console.
log(tostring.
('***x'))
;// [object string]
console.
log(tostring.
(123))
;// [object number]
console.
log(tostring.([
]));
// [object array]
console.
log(tostring.()
);// [object object]
console.
log(tostring.
(undefined));
// [object undefined]
console.
log(tostring.
(null))
;// [object null]

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