JavaScript Code Notes

https://github.com/masumkhan081/javascript-code-notes

Topic-by-topic JavaScript reference, ordered by prerequisite chain (easy → hard). One topic per folder. Numbered prefixes preserve study order. MERN-stack focused — language features and interview edge cases first.

Directory layout

Language fundamentals (01–04)

#	Folder	Topic
01	01_basic/	primitives, types, syntax
02	02_operators-coercion/	**== vs ===, truthy/falsy, ??, ?., ??= **
03	03_hoisting/	var/let/const, TDZ, function/class hoisting
04	04_scope-this/	lexical scope, this, call/apply/bind

Data & ES6 (05–08)

#	Folder	Topic
05	05_array/	array ops, reduce patterns
06	06_spread-rest/	spread/rest operator
07	07_object-model/	hasOwn/in, property descriptors, Proxy/Reflect, Map vs Object
08	08_object-prototype/	prototype chain, constructor functions, prototype pollution

Functions & functional patterns (09–13)

#	Folder	Topic
09	09_function/	arrow vs regular, HOF, IIFE, generators, memoization, recursion
10	10_callback/	callbacks, callback hell, sync vs async
11	11_closure/	closure basics, scope capture, memory leaks, interview Qs
12	12_curry/	currying, partial application
13	13_module-system/	CJS cache, CJS circular, ESM live bindings, ESM top-level await

OOP (14–24)

#	Folder	Topic
14	14_oop-class-object/	class syntax, instances
15	15_oop-encapsulation/	private fields, getters/setters
16	16_oop-inheritance/	extends, super, prototype chain, anti-patterns
17	17_oop-polymorphism/	method overriding, dispatch
18	18_oop-static-members/	static methods, static blocks
19	19_oop-abstract-class/	abstract pattern in JS
20	20_oop-composition-vs-inheritance/	mixins, React composition, perf, testing
21	21_oop-mixins/	mixin patterns
22	22_oop-solid/	SOLID principles in JS
23	23_oop-di/	dependency injection
24	24_oop-decorators/	decorator patterns

Async (25–28)

#	Folder	Topic
25	25_promise/	promise lifecycle, chaining, all/race/any/allSettled, microtasks, real-world patterns
26	26_async-await/	basics, sequential vs parallel, top-level await, cancellation, memory leaks, async generators
27	27_async-control/	concurrency limiting, AbortController timeout, retry+backoff
28	28_error-handling/	sync/async errors, try/catch patterns

Runtime & Node (29–34)

#	Folder	Topic
29	29_memory-gc/	closure retention, listener leaks, WeakMap private state
30	30_regex/	regex patterns
31	31_buffer-encoding/	string vs buffer length, UTF-8 chunk boundary, base64
32	32_node-event-loop/	nextTick vs promise vs timer, starvation, phases
33	33_node-runtime/	unhandled rejection, EventEmitter errors, graceful shutdown, worker threads
34	34_node-streams/	readFile vs stream, backpressure, pipeline error handling

Senior-level / interview-prone subtopics are bolded. Where present, files are numbered 1-, 2-, 3- inside their folder for in-topic study order.

Running examples

node 02_operators-coercion/1-equality-and-coercion.js
node 25_promise/4-promise-chaining.js
node 32_node-event-loop/1-nexttick-vs-promise-vs-timer.js

node is the only runtime needed for most files. Browser-DOM examples may exist in older .html files in 01_basic/.

External references

• MDN JavaScript
• You Don't Know JS
• JavaScript.info
• Node.js docs
• ECMAScript spec