const isNegative = (n) => Math.sign(n) === -1;// Orconst isNegative = (n) => n < 0;
const isNegative = (n: number): boolean => Math.sign(n) === -1;// Orconst isNegative = (n: number): boolean => n < 0;
isNegative(-3); // trueisNegative(8); // false