JavaScript界において、もはや「伝統芸能」や「言語の黒歴史」として最も愛され（？）、そしてネタにされ続けている伝説的バグですね！ 「null（無）を調べているのに object（オブジェクト）と主張してくる」という、JavaScript誕生の数日間に起きたドラマと ...

JavaScript では、変数にどんなデータが入っているかを「実行時」に調べたい場面があります。 そんなときに使えるのが typeof 演算子 です。 typeof は JavaScript で値の「データ型（型）」を調べる演算子 です。

Note: that name is the function//constructor name, or Annonymous, Note: name is always capital (first letter), or left as defined by the function, otherwise unexpected letter casing could go wrong.

typeof is an operator that is used to identify the type of any object in javascript. It returns a value that is string. So you can compare any string value from returned value of typeof. // Examples ...

You can use typeof to check the data structure, or type, of a variable. This is useful in debugging when working with multiple data types. If you think you're adding two numbers, but one is actually a ...

Reason: NaN means "Not a Number," but JavaScript considers it a special value of the number data type. So, typeof NaN returns "number" because its meaning is invalid numerical result, not a separate ...