Remove duplicate lines

Keep the first occurrence of every exact line while normalizing CRLF to LF.

JavaScript Version 1.0.0 · MIT · .md

function uniqueLines(value) { return [...new Set(value.split(/\r?\n/))].join('\n'); }

Input & expected output

"accepted\ndelivered\naccepted"

"accepted\ndelivered"

The edge case

""

""

Know the limits

• Whitespace and case matter. One empty line is retained; line endings become LF.

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.