30-seconds-of-code/snippets/isNumber.md

isNumber

Checks if the given argument is a number.

Use typeof to check if a value is classified as a number primitive. Because typeof NaN is equal to number, the val === val is for protection. NaN compares unequal (via ==, !=, ===, and !==) to any other value, including to another NaN value.

const isNumber = val => typeof val === 'number' && val === val;

isNumber(1); // true
isNumber('1'); // false
isNumber(NaN); // false