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How JavaScript Runs: JavaScript: Uncharted

Courses JavaScriptHow JavaScript Runs

How JavaScript Runs

Trace the event loop and its queues, reason about hoisting, and explain coercion and memory references.

JavaScript
Unit 17 of 20
20 lessons
166 min
420 XP

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Lessons

20 total

1One Cook, One KitchenExplain how one JavaScript thread can coordinate work that appears concurrent.InteractiveConcept6 min20 XPOpen
2The Call Stack, LiveTrace how three nested function calls push and pop stack frames.InteractiveConcept7 min20 XPOpen
3Blocking the KitchenDemonstrate that synchronous work delays a timer callback from running.CodeConcept10 min20 XPOpen
4The Waiting AreaIdentify where a ready timer callback waits and when it may enter the stack.InteractiveConcept7 min20 XPOpen
5Two Timers RacePredict synchronous logs and two differently delayed timer callbacks.InteractiveConcept7 min20 XPOpen
6The Express LanePredict why promise reactions run before ready timer tasks.InteractiveConcept7 min20 XPOpen
7Prove the Express LaneRun sync, promise, and timer logs that reveal queue priority.CodeConcept8 min20 XPOpen
8One Full CycleOrder the stack and queue phases of one event-loop cycle.InteractiveConcept7 min20 XPOpen
9The Grand PredictionPredict an event-loop trace with sync logs, two promise reactions, and two timers.InteractiveConcept10 min20 XPOpen
10Starving the QueueBuild a bounded recursive microtask chain that delays a ready timer task.CodeConcept10 min20 XPOpen
11Hoisting: Two StoriesContrast early function-declaration calls with a let binding in its temporal dead zone.InteractiveConcept8 min20 XPOpen
12The Dead ZoneMove a lexical declaration before its first read to avoid the temporal dead zone.CodeConcept8 min20 XPOpen
13var, the ElderPredict var initialization and function scope across a block.InteractiveConcept8 min20 XPOpen
14Coercion Rules of ThumbMatch three mixed-type expressions to the values produced by implicit coercion.InteractiveConcept8 min20 XPOpen
15Explicit Beats ImplicitNormalize mixed input with Number, String, and Boolean before comparing it.CodeConcept9 min20 XPOpen
16Two Kinds of MemoryPredict independent primitive copies and shared object references across four mutations.InteractiveConcept8 min20 XPOpen
17Prove the Shared BoxObserve shared mutation through an alias, then separate future mutations with a copy.CodeConcept9 min20 XPOpen
18The Cleanup CrewIdentify when an object becomes unreachable and what garbage collection guarantees.InteractiveConcept7 min20 XPOpen
19Narrate One ClickExplain how the stack, queues, and event loop handle a button callback that schedules a timer.InteractiveConcept10 min20 XPOpen
20How JavaScript Runs Mastery CheckEvaluate difficult predictions about scheduling, declarations, coercion, and references.InteractiveMastery check12 min40 XPOpen

Asynchronous JavaScript Data Structures