Check if a string contains only letters

JavaScript

const isAlpha = (str) => /^[A-Z]+$/i.test(str)

TypeScript

const isAlpha = (str: string): boolean => /^[A-Z]+$/i.test(str)

Examples

isAlpha('helloworld') // true
isAlpha('HelloWorld') // true
isAlpha('hello world') // false
isAlpha('0123456789') // false