JavaScript Interview Preparation Guide
JavaScript is the first round at almost every frontend interview. Here's exactly what to study and how to practise it.
The topics that come up
Scope and closures, the this keyword, prototypes and inheritance, the event loop (micro vs macrotasks), promises and async/await, type coercion and equality, and the array methods (map/filter/reduce). These account for the vast majority of first-round questions.
How to practise
Two things beyond reading: predict the output of tricky snippets (hoisting, closures in loops, promise ordering), and implement the classics from scratch — debounce, throttle, curry, a polyfill for map/bind, deep clone. Being able to code these live is a strong signal.
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80+ Q&A, coding patterns, polyfills and output traps — with structured answers in the JavaScript Interview Kit.
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- Do I need to know DSA for a JS frontend role?
- Light DSA plus a few patterns (frequency counter, two pointers, sliding window, recursion) covers most frontend rounds. Deep algorithms matter more at big-tech.
- How long should I prepare?
- 3–5 days of focused prep on the core topics, plus practice on output questions and must-implement utilities.