How to change a String's Case in JavaScript

Strings can be capitalized using String.toUpperCase
For instance;

const str = 'John swana'

str.toUpperCase()

// 'JOHN SWANA'

String.toLowerCase turns strings to their small letters or 'lowerCase'

const strr = "Lorem ipsum"
strr.toLowerCase()

// lorem ipsum

Numbers are not converted, they remain constant, untouched and unchanged.

'65'.toLowerCase()

// '65'