用isNaN函数判断是否是Number中的坑

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("123ABC"); // true: parseInt("123ABC") is 123 but Number("123ABC") is 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 // dates isNaN(new Date()); // false isNaN(new Date().toString()); // true // 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