Check if a date is a weekend

Return true when a YYYY-MM-DD date falls on a Saturday or Sunday.

JavaScript Version 1.0.0 · MIT · .md

function isWeekend(date) { return new Date(date).getUTCDay() % 6 === 0; }

Input & expected output

"2026-10-31"

true

The edge case

"2026-10-30"

false

Know the limits

• The date is read as a UTC calendar day, so the result does not depend on the machine’s time zone. The original used local time on a Date object.
• Saturday–Sunday weekends only; other calendars need their own rule.

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

• Check whether all values are equal — Compare every item with the first using Object.is.
• Check whether an object is empty — Check for own enumerable string keys on a JSON object.
• Check whether an integer is even — Test parity for safe integers, including zero and negative values.