Primitives vs references
Trivia EasyExplain stack-style value copying vs reference-style mutation behavior.
Practice trivia
8 min
JavaScript Mastery Crash Track
Coercion rules that actually matter
Trivia EasyReason about Number/String/Boolean coercion with concrete edge cases.
Practice trivia
10 min
Truthy and falsy checkpoints
Trivia EasyList all falsy values and explain why objects stay truthy.
Practice trivia
6 min
Predict output: equality traps
Predict Output EasyPredict results for loose/strict comparisons before running code.
Run prediction drills
10 min
Coding drill: control flow reliability
Coding EasyImplement core loop logic cleanly with deterministic branching.
Practice coding
15 min
Coding drill: frequency map
Coding EasyBuild a reusable counting helper over arrays and strings.
Practice coding
18 min
Checkpoint: Foundations gate
Checkpoint EasyPass a short mixed drill before unlocking Functions and Scope.
Run checkpoint
12 min
Hoisting without myths
Trivia MediumState exactly what is hoisted and what is not for var/let/const/functions.
Practice trivia
10 min
Predict output: Temporal Dead Zone
Predict Output MediumIdentify TDZ runtime failures from small snippets.
Run prediction drills
10 min
Closure fundamentals
Trivia MediumExplain lexical scope capture with practical use cases.
Practice trivia
10 min
Predict output: var loop callbacks
Predict Output MediumExplain why var/let differ in asynchronous loop callbacks.
Run prediction drills
12 min
Coding drill: closure counter
Coding MediumImplement encapsulated state with function factories.
Practice coding
20 min
Coding drill: custom bind
Coding MediumRecreate bind semantics for interview-level understanding.
Practice coding
24 min
Checkpoint: Functions and Scope gate
Checkpoint MediumValidate closures/hoisting under mixed trivia + coding pressure.
Run checkpoint
14 min
Prototype chain lookup
Trivia MediumTrace property resolution across prototype boundaries.
Practice trivia
10 min
Class syntax vs prototype model
Trivia MediumDifferentiate syntax sugar from runtime behavior.
Practice trivia
10 min
Predict output: this binding
Predict Output MediumApply call-site rules for this in regular vs arrow functions.
Run prediction drills
12 min
Property descriptors and mutability
Trivia MediumUse writable/configurable/enumerable flags correctly.
Practice trivia
10 min
Coding drill: new operator polyfill
Coding HardImplement object creation with prototype wiring manually.
Practice coding
26 min
Coding drill: deep freeze utility
Coding HardRecursively enforce immutability over nested objects.
Practice coding
24 min
Checkpoint: Objects and Prototypes gate
Checkpoint MediumConfirm this/prototype reasoning before async-heavy modules.
Run checkpoint
14 min
Predict output: event loop ordering
Predict Output HardOrder logs across sync code, microtasks, and timers.
Run prediction drills
14 min
Microtask vs macrotask rules
Trivia HardExplain scheduling and starvation risks succinctly.
Practice trivia
12 min
Promise combinator trade-offs
Trivia HardChoose all/allSettled/race/any by failure behavior.
Practice trivia
12 min
Async error handling strategy
Trivia HardAvoid swallowed failures while keeping flows readable.
Practice trivia
10 min
Coding drill: retry wrapper
Coding HardImplement retry with bounded attempts and backoff behavior.
Practice coding
28 min
Coding drill: timeout wrapper
Coding HardRace async work against timeout with clean rejection semantics.
Practice coding
24 min
Checkpoint: Async and Event Loop gate
Checkpoint HardPass mixed async reasoning before browser-focused drills.
Run checkpoint
16 min
Event propagation model
Trivia MediumCapture, target, bubble phases and practical debugging.
Practice trivia
10 min
Event delegation trade-offs
Trivia MediumChoose delegation boundaries for dynamic lists safely.
Practice trivia
10 min
Abort in-flight requests
Trivia MediumUse AbortController to prevent stale network writes.
Practice trivia
10 min
CORS basics for frontend interviews
Trivia MediumExplain preflight, allowed origins, and credentials constraints.
Practice trivia
10 min
Coding drill: debounce
Coding MediumImplement trailing and optional leading behavior correctly.
Practice coding
20 min
Coding drill: throttle
Coding MediumControl execution rate while preserving user intent.
Practice coding
20 min
Coding drill: searchable list
Coding HardCombine delegation and debounced input for a realistic UI task.
Practice coding
24 min
Checkpoint: Browser Practice gate
Checkpoint HardValidate browser APIs and utility implementation quality.
Run checkpoint
16 min
Memory leak diagnosis
Trivia HardIdentify leak roots in listeners, closures, and retained DOM nodes.
Practice trivia
12 min
Immutability trade-offs
Trivia HardBalance readability, safety, and performance in state updates.
Practice trivia
12 min
ESM vs CommonJS in practice
Trivia HardExplain import/export execution and interop behavior.
Practice trivia
10 min
Coding drill: map/filter/reduce polyfills
Coding HardImplement core array method behavior and callback contracts.
Practice coding
30 min
Coding drill: LRU cache
Coding HardBuild eviction strategy with predictable O(1)-style operations.
Practice coding
34 min
Coding drill: tiny reactive store
Coding HardDesign subscribe/unsubscribe/update semantics with cleanup safety.
Practice coding
32 min
Final checkpoint: JavaScript Mastery pass
Checkpoint HardRun a final mixed simulation and capture weak spots for next cycle.
Run final simulation
20 min
Foundations
Unlock rule: Start here.
This module teaches
- Read and reason about values without guessing coercion behavior.
- Distinguish reference vs primitive updates in interview snippets.
- Write small utility transforms with clear runtime behavior.
Common mistakes
- Relying on memorized tricks instead of deterministic value rules.
- Mixing strict and loose equality without clear intent.
- Skipping edge cases in basic loops and reducers.
Scoring model
Trivia + predict output35%
Coding drills65%