➕typeof

type of a value.

• JS ⟩ value ⟩ type ⟩ name ⟩ typeof

• JS ⟩ operator ⟩ unary ⟩ typeof

(unary operator) determines the type of a value. (👉 type name)

🧨 雷區

⛔typeof let/const/class in TDZ gets an error❗️

🗺️ 圖解

• 👉 compare： typeName()

#	Result	Types
1	'boolean'	Boolean
2	'string'	String
3	'number'	Number
4	'bigint'	BigInt
5	'symbol'	Symbol
6	'undefined'	undefined
7	'function'	function method arrow function generator function class
8	'object'	null ( null is a primitive❗️) any other objects, like Object Array RegExp Date object literal instances of class ...

⭐️ 重點

typeof null === "object"    // true

👥 相關

• typeName() - refined version of typeof.

📘 手冊

• typeof