最終更新:2019-05-17 (金) 18:26:02 (1777d)
数値?NaN
Top / NaN
Not a Number
JavaScript
- NaN == NaN はfalse→isNaNで調べる
isNaN(NaN); // true isNaN(undefined); // true isNaN({}); // true isNaN(true); // false isNaN(null); // false isNaN(37); // false // strings isNaN("37"); // false: "37" is converted to the number 37 which is not NaN isNaN("37.37"); // false: "37.37" is converted to the number 37.37 which is not NaN isNaN(""); // false: the empty string is converted to 0 which is not NaN isNaN(" "); // false: a string with spaces is converted to 0 which is not NaN // This is a false positive and the reason why isNaN is not entirely reliable isNaN("blabla") // true: "blabla" is converted to a number. Parsing this as a number fails and returns NaN
C♯
- doouble.NaN?
- Double.isNaN