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🔮 JS Output Questions

72 predict-the-output questions — the category that trips up even experienced JS devs in real interviews.

Goal

Predict the output of any hoisting, closure, async, coercion, or prototype question without running it.

Output Questions: Hoisting & Scope

Predict the output — var/let/const hoisting, TDZ, function declaration vs expression, and block scope gotchas.

medium ⏱ 25m 02

Output Questions: Closures & Loops

Predict the output — closure capture, stale closures, IIFE patterns, loop bugs, and memoization gotchas.

medium ⏱ 25m 03

Output Questions: Event Loop & Async

Predict execution order — setTimeout vs Promise vs queueMicrotask, async/await unwrapping, and nested async patterns.

hard ⏱ 30m 04

Output Questions: this & Prototype Chain

Predict the output — implicit/explicit/new binding, arrow functions, prototype lookup, class inheritance, and the classic this-loss traps.

hard ⏱ 28m 05

Output Questions: Coercion, Operators & Equality

Predict the output — type coercion puzzles, == vs ===, + operator surprises, typeof edge cases, and bitwise/logical traps.

hard ⏱ 25m 06

Output Questions: Mixed & Advanced

Predict the output — generators, class edge cases, Array methods, Object tricks, Symbol, and multi-concept combinations.