ReturnTrue
Find the shortest input that makes each JavaScript function return true
ReturnTrue is a set of short JavaScript puzzles. Each level shows you a function, and you must type an input that makes it return true. The catch is that your input should be as short as possible. Your length is counted as strokes, and a leaderboard ranks players by levels solved and total strokes.
Free · No login · Browser · Advanced
About ReturnTrue
The puzzles rely on the strange corners of JavaScript, such as type coercion, NaN and other edge cases. It suits experienced JavaScript developers who enjoy code golf.
It runs in the browser with no sign-up. To keep your progress or move to another browser, you bookmark a personal link. Players can also create their own levels.
On Breakpoint since 23 Oct 2026.