Test Your JavaScript Skills
Test your JavaScript across core syntax and coercion, functions/scope/closures and this, objects/arrays and data structures, and the event loop/async/prototype idioms. 30 code-reading questions, instant score by category, free with no signup.
What is the JavaScript Test?
This is a scenario-based JavaScript test: 30 short code snippets, each followed by a question about what actually happens when it runs. A var captured inside a loop’s callbacks that all read the same final value instead of the one you expected. An == comparison that quietly coerces types before comparing them. A spread copy that looks deep but only copies the top level. You pick the answer that matches what the code actually prints or does, not what looks like it should happen.
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The 30 questions cover four areas — core syntax and coercion, functions/scope/closures and this, objects/arrays and data structures, and the event loop/async/prototype idioms. Those four are the places where reading code and running code quietly diverge, and where a job posting’s Strong JavaScript usually turns out to mean something specific once you are in the interview. You get a score in each area, so a weak spot shows up as a weak spot rather than as a lower total.
It takes about nine minutes, there is no signup, and there is no code to write or run — every question is read-and-predict, the same way a senior engineer reviews a pull request. Knowing the syntax and knowing what a specific snippet does at runtime are different skills, and this measures the second one.
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