Check if a string is a hexadecimal number

JavaScript version
const isHexadecimal = (str) => /^[A-F0-9]+$/i.test(str);
// Or
const isHexadecimal = (str) => str.split('').every((c) => '0123456789ABCDEFabcdef'.indexOf(c) !== -1);
TypeScript version
const isHexadecimal = (str: string): boolean => /^[A-F0-9]+$/i.test(str);
// Or
const isHexadecimal = (str: string): boolean => str.split('').every((c) => '0123456789ABCDEFabcdef'.indexOf(c) !== -1);
Examples
isHexadecimal('123'); // true
isHexadecimal('A1B2C3'); // true
isHexadecimal('#123'); // false