JS Is Weird
Predict the output of twenty-five quirky JavaScript expressions
JS Is Weird is a quiz of twenty-five odd JavaScript expressions. For each one you choose what it evaluates to, and the quiz then explains why. The expressions lean on type coercion, operator precedence, odd literals and other legacy behaviour.
Free · No login · Browser · Intermediate
About JS Is Weird
It trains a precise mental model of how JavaScript evaluates code, including the corners most people avoid. It suits JavaScript developers who think they know the language well.
It runs in the browser, takes a few minutes, and is free with no account.
On Breakpoint since 25 Oct 2026.
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