Capitalize a string

Uppercase the first Unicode code point and preserve the remaining text.

JavaScript Version 1.0.0 · MIT · .md

function capitalize(value) { const [first, ...rest] = Array.from(value); return first ? first.toUpperCase() + rest.join('') : ''; }

Input & expected output

"hello, developer"

"Hello, developer"

The edge case

""

""

Know the limits

• Uppercasing can expand a character, such as ß into SS. This is not locale-aware title casing.

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

• Reverse a string — Reverse Unicode code points without splitting surrogate pairs.
• Check a palindrome — Compare a string with its code-point reversal.
• Create a simple URL slug — Normalize a Latin-text label into lowercase ASCII words separated by hyphens.