JavaScript String Case

toUpperCase and toLowerCase return a new string in a different case.

Neither one changes the original, because strings cannot be changed.

The most common use is comparing text without caring about case.

Example

const name = "Ada";

console.log(name.toUpperCase());
console.log(name);

The original is untouched, as always with strings.

Changing Case

toUpperCase() returns an upper case copy.

toLowerCase() returns a lower case copy.