Swap case of characters in a string

JavaScript version
const swapCase = (str) =>
str
.split('')
.map((c) => (c === c.toLowerCase() ? c.toUpperCase() : c.toLowerCase()))
.join('');
TypeScript version
const swapCase = (str: string): string =>
str
.split('')
.map((c) => (c === c.toLowerCase() ? c.toUpperCase() : c.toLowerCase()))
.join('');
Examples
swapCase('Hello World'); // 'hELLO wORLD'