Swap case of characters in a string

Uppercase lowercase letters and lowercase the rest.

JavaScript Version 1.0.0 · MIT · .md

function swapCase(text) { return Array.from(text).map(char => char === char.toLowerCase() ? char.toUpperCase() : char.toLowerCase()).join(''); }

Input & expected output

"Hello World"

"hELLO wORLD"

The edge case

"ß"

"SS"

Know the limits

• Case mapping can change length: ß uppercases to SS.

The function above is the implementation used by the lab. The lab validates JSON types and caps size before execution; include equivalent validation when accepting untrusted input in your application.

Keep exploring

• Capitalize a string — Uppercase the first Unicode code point and preserve the remaining text.
• Reverse a string — Reverse Unicode code points without splitting surrogate pairs.
• Check a palindrome — Compare a string with its code-point reversal.