JavaScript Mastery in 14 Days

Master the most frequently asked JavaScript interview patterns: debounce/throttle, promises, event emitters, polyfills, closures, cloning, and functional programming. Covers every top polyfill asked at Google, Meta, Amazon, and top startups.

14 days

Beginner

38 milestones

Your Progress

0 of 38 milestones completed

Daily Plan

38 total

Day 1: Timers + Rate Limiting I

FOUNDATIONFREE

0 of 2 completed

Core UI primitives: debounce + throttle. Nail signatures + edge cases.

TimersClosures

Debounce Function

Problem

Throttle Function

Problem

Day 2: Timers + Rate Limiting II

INTERMEDIATEFREE

0 of 2 completed

Enhanced variants = where most candidates fail.

Trailing/LeadingCancel/Flush

Advanced Debounce Function

Problem

Enhanced Throttle Function

Problem

Day 3: Closures + Functional Patterns

FOUNDATIONFREE

0 of 3 completed

Counter closure, once, compose, and pipe. Core FP building blocks asked at every company.

ClosuresFPComposition

Day 4: Eventing I

FOUNDATIONFREE

0 of 2 completed

Classic interview question. Contracts matter.

PubSubData Structures

Event Emitter

Problem

Enhanced Event Emitter

Problem

Day 5: Eventing II + Memoization

INTERMEDIATEFREE

0 of 2 completed

Advanced emitter + memoization. Both test closure mastery and cache invalidation.

Edge CasesCaching

Advanced Event Emitter

Problem

Memoization

Problem

Day 6: Promises I (Combinators)

INTERMEDIATEFREE

0 of 2 completed

Promise.all + race = core async semantics.

PromisesDeterminism

Promise.all (Polyfill)

Problem

Promise.race

Problem

Day 7: Promises II (Variants)

INTERMEDIATEFREE

0 of 2 completed

These separate "knows promises" vs "really knows promises."

AllSettledAny

Promise.any

Problem

Promise.allSettled

Problem

Day 8: Promises III (Control Flow)

ADVANCEDFREE

0 of 3 completed

Real-world async: limit concurrency, retry with backoff, enforce timeouts.

ConcurrencyRetriesTimeouts

Promise Limit - K Parallel Tasks

Problem

Promise Retry with Backoff

Problem

Promise Timeout

Problem

Day 9: Function Polyfills

INTERMEDIATEFREE

0 of 3 completed

bind, call, apply are top-3 asked polyfills. Tests understanding of this binding and prototype chain.

PolyfillsthisPrototypes

Function.prototype.bind

Problem

Function.prototype.call

Problem

Function.prototype.apply

Problem

Day 10: Cloning + Equality

INTERMEDIATEFREE

0 of 3 completed

Deep clone + deep equal. Tests understanding of reference types, circular refs, and edge cases.

ObjectsReferencesComparison

Deep Clone

Problem

Deep Equal

Problem

Deep Clone with Circular References

Problem

Day 11: Array Polyfills

FOUNDATIONSTREAK UNLOCK

0 of 3 completed

map, filter, reduce are the most asked array polyfills. Tests callback patterns and accumulator logic.

PolyfillsArray Methods

Array.prototype.map (Polyfill)

Problem

Array.prototype.filter (Polyfill)

Problem

Array.prototype.reduce (Polyfill)

Problem

Day 12: Object + Operator Polyfills

INTERMEDIATEPRO

0 of 3 completed

instanceof, new, Object.assign = tests deep JS internals knowledge.

PolyfillsOperatorsInternals

Locked

Implement instanceof

Problem

Implement new Operator

Problem

Object.assign Polyfill

Problem

Day 13: Utility Functions

ADVANCEDPRO

0 of 3 completed

Lodash-style utilities: get, group-by, chunk, flatten. Asked at every top company.

UtilsPath AccessData

Locked

Lodash _.get

Problem

Group By

Problem

Chunk Array

Problem

Day 14: DOM + Advanced Capstone

INTERVIEWPRO

0 of 5 completed

Capstone: DOM traversal + JSON serialization + advanced async. Proves production-grade JS mastery.

DOMTraversalSerializationCapstone

JS Track FinisherProfile Highlight

Locked

Get DOM Tree Height

Problem

Traverse DOM Level by Level

Problem

JSON.stringify - Simple

Problem

JSON.parse - Simple

Problem

Pipe Function

Problem

Start First Milestone

Back to Learning Paths

JavaScript Mastery in 14 Days

14 days

Beginner

38 milestones

Your Progress

0 of 38 milestones completed

Daily Plan

38 total

Day 1: Timers + Rate Limiting I

FOUNDATIONFREE

0 of 2 completed

Core UI primitives: debounce + throttle. Nail signatures + edge cases.

TimersClosures

Debounce Function

Problem

Throttle Function

Problem

Day 2: Timers + Rate Limiting II

INTERMEDIATEFREE

0 of 2 completed

Enhanced variants = where most candidates fail.

Trailing/LeadingCancel/Flush

Advanced Debounce Function

Problem

Enhanced Throttle Function

Problem

Day 3: Closures + Functional Patterns

FOUNDATIONFREE

0 of 3 completed

Counter closure, once, compose, and pipe. Core FP building blocks asked at every company.

ClosuresFPComposition

Counter Function with Closure

Problem

Once Function

Problem

Compose Function

Problem

Day 4: Eventing I

FOUNDATIONFREE

0 of 2 completed

Classic interview question. Contracts matter.

PubSubData Structures

Event Emitter

Problem

Enhanced Event Emitter

Problem

Day 5: Eventing II + Memoization

INTERMEDIATEFREE

0 of 2 completed

Advanced emitter + memoization. Both test closure mastery and cache invalidation.

Edge CasesCaching

Advanced Event Emitter

Problem

Memoization

Problem

Day 6: Promises I (Combinators)

INTERMEDIATEFREE

0 of 2 completed

Promise.all + race = core async semantics.

PromisesDeterminism

Promise.all (Polyfill)

Problem

Promise.race

Problem

Day 7: Promises II (Variants)

INTERMEDIATEFREE

0 of 2 completed

These separate "knows promises" vs "really knows promises."

AllSettledAny

Promise.any

Problem

Promise.allSettled

Problem

Day 8: Promises III (Control Flow)

ADVANCEDFREE

0 of 3 completed

Real-world async: limit concurrency, retry with backoff, enforce timeouts.

ConcurrencyRetriesTimeouts

Promise Limit - K Parallel Tasks

Problem

Promise Retry with Backoff

Problem

Promise Timeout

Problem

Day 9: Function Polyfills

INTERMEDIATEFREE

0 of 3 completed

bind, call, apply are top-3 asked polyfills. Tests understanding of this binding and prototype chain.

PolyfillsthisPrototypes

Function.prototype.bind

Problem

Function.prototype.call

Problem

Function.prototype.apply

Problem

Day 10: Cloning + Equality

INTERMEDIATEFREE

0 of 3 completed

Deep clone + deep equal. Tests understanding of reference types, circular refs, and edge cases.

ObjectsReferencesComparison

Deep Clone

Problem

Deep Equal

Problem

Deep Clone with Circular References

Problem

Day 11: Array Polyfills

FOUNDATIONSTREAK UNLOCK

0 of 3 completed

map, filter, reduce are the most asked array polyfills. Tests callback patterns and accumulator logic.

PolyfillsArray Methods

Array.prototype.map (Polyfill)

Problem

Array.prototype.filter (Polyfill)

Problem

Array.prototype.reduce (Polyfill)

Problem

Day 12: Object + Operator Polyfills

INTERMEDIATEPRO

0 of 3 completed

instanceof, new, Object.assign = tests deep JS internals knowledge.

PolyfillsOperatorsInternals

Locked

Implement instanceof

Problem

Implement new Operator

Problem

Object.assign Polyfill

Problem

Day 13: Utility Functions

ADVANCEDPRO

0 of 3 completed

Lodash-style utilities: get, group-by, chunk, flatten. Asked at every top company.

UtilsPath AccessData

Locked

Lodash _.get

Problem

Group By

Problem

Chunk Array

Problem

Day 14: DOM + Advanced Capstone

INTERVIEWPRO

0 of 5 completed

Capstone: DOM traversal + JSON serialization + advanced async. Proves production-grade JS mastery.

DOMTraversalSerializationCapstone

JS Track FinisherProfile Highlight

Locked

Get DOM Tree Height

Problem

Traverse DOM Level by Level

Problem

JSON.stringify - Simple

Problem

JSON.parse - Simple

Problem

Pipe Function

Problem

Start First Milestone