作者freeman371 (自由人371)
看板Ajax
標題[問題] Why NaN and Infinity are classified as the type of numbe
時間Fri Jul 21 14:10:51 2017
I have practiced Javascript for a long long time,
and there's always a contradiction, which has confused me so much.
That is, why NaN and Infinity are both types of “number”?
In mathematics,“Infinity”is just a concept, not a number.
“NaN”means“Not a number”on its literal meaning.
Obviously those are not“numbers.”
However, in Javascript, both“NaN”and“Infinity”are“number.”
You can try it like below:
typeof NaN // Returns“number”
typeof Infinity // Returns“number”
So what's the reason?
Could someone tell me the reason about this weird contradiction?
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1F：→ ssccg: 不然你覺得是什麼type? 07/21 14:19
2F：→ ssccg: 實作上來說這些只是特別的數字，可參考IEEE754 07/21 14:32
3F：推 DolphinLinn: NaN is number type, and NaN != NaN 07/21 22:58
4F：推 aspdoctor: 白馬是馬，白馬也非馬，就這個意思 07/22 01:27
5F：推 Qiqi: 樓上不如講 色即是空，空即是色 07/24 10:07
6F：推 visa9527: 就像 '' 也是 string 啊，明明就是空的東西 07/24 15:20
7F：推 hijkxyzuw: 浮點數裡有定義 NaN ，所以在 C 裡也能用。 07/25 22:33
8F：推 VdustR: null 也是 object 阿 07/30 03:24