Learning paths · Skills · Intermediate

JavaScript: how it really runs

What the engine actually does with your code, from the call stack to the event loop, one picture at a time.

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01FoundationsHow one piece of code runs

02AsyncWaiting without blocking

03Under the hoodEngines, memory and Node

04Next: system designSame ideas, at service scale

BackpressureLibrary ↗Queues that fill faster than they drain: the event loop's problem, at system scale.

TimeoutLibrary ↗A promise that never settles is a request that never ends. Put a limit on waiting.

Publish/subscribeLibrary ↗Event listeners and emitters, scaled out to many services.

01FoundationsHow one piece of code runs0/4
02AsyncWaiting without blocking0/4
03Under the hoodEngines, memory and Node0/4
04Next: system designSame ideas, at service scale

Where this path leads

Node.js: how the server side runs →What happens between your JavaScript and the operating system: the loop's phases, its private queues, the thread pool, streams, and threads of your own.