30-seconds-of-code/snippets/js/s/swap-case.md

title, type, language, tags, cover, dateModified

title	type	language	tags	cover	dateModified
Swapcase string	snippet	javascript	string	mountain-lake-2	2020-11-15T13:09:03+02:00

Creates a string with uppercase characters converted to lowercase and vice versa.

• Use the spread operator (...) to convert str into an array of characters.
• Use String.prototype.toLowerCase() and String.prototype.toUpperCase() to convert lowercase characters to uppercase and vice versa.
• Use Array.prototype.map() to apply the transformation to each character, Array.prototype.join() to combine back into a string.
• Note that it is not necessarily true that swapCase(swapCase(str)) === str.

const swapCase = str =>
  [...str]
    .map(c => (c === c.toLowerCase() ? c.toUpperCase() : c.toLowerCase()))
    .join('');

swapCase('Hello world!'); // 'hELLO WORLD!'