Capitalize a string

JavaScript version

const capitalize = (str) => `${str.charAt(0).toUpperCase()}${str.slice(1)}`;

// Or
const capitalize = ([first, ...rest]) => `${first.toUpperCase()}${rest.join('')}`;

// Or
const capitalize = (str) => str.replace(/^([a-z])/, (first) => first.toUpperCase());

TypeScript version

const capitalize = (str: string): string => `${str.charAt(0).toUpperCase()}${str.slice(1)}`;

// Or
const capitalize = ([first, ...rest]: string): string => `${first.toUpperCase()}${rest.join('')}`;

// Or
const capitalize = (str: string): string => str.replace(/^([a-z])/, (first) => first.toUpperCase());

Examples

capitalize('hello world'); // 'Hello world'