How memory leaks happen and how the Mark-and-Sweep algorithm works.
Timothy was staring at the dashboard he was building. It was getting slow. ...
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Hi, thanks for this post.
I really like your explaining interesting concepts in stories.
in a world where the RAMs are more abundant and cheaper, and since web devs work on laptops/servers not chips, a typical JS developer may easily be inclined to not-think about memory management -true, it is not as C++ development in the end- but i suppose it can affect web performance for certain cases.
I suppose event handlers are the easiest trap, as you defined. In react, as they are mostly defined in useEffects, it must be cared and removed during the unmounting of the component, which is something that can be forgotten in haste (speaking from experience)
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Keep up the great work!
thank you, Sloan!
it's a privilege to be part of the dev.to community.
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The way you frame GC as “tracing invisible connections” instead of deleting objects directly makes the whole Mark-and-Sweep idea click instantly. The event listener + closure example is especially good — that’s exactly the kind of leak many developers hit without realizing why memory keeps growing.
I also like that the takeaway isn’t “GC is magic” but “GC is predictable if you understand reachability.” That mindset shift alone can save hours of debugging sluggish apps.
Great write-up. Curious if you’re planning to cover other real-world leak patterns next (intervals, detached DOM nodes, caches, etc.) — this series is super easy to follow and very practical.
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Please, correct me if I'm wrong, but I dare to say that functional programming helps to avoid these traps. The function considered wouldn't have been implemented in pure functional programming.
Also, I'm a Svelte user, and the framework/compiler itself helps to avoid these circumstances.
In the end, if we follow a good coding structure (which I believe functional programming brings) and rely on the great tools we have, we can code with a light heart, without overthinking issues like GC, but understanding it is a must; therefore, thanks for the article.
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A very clear and concise explanation of a complex topic. Garbage collection is one of those features we often take for granted until things go wrong. Thanks for sharing Aaron!
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What I like about this is that it doesn’t treat the GC as some mystical background daemon — it treats it like a graph problem. Once you see memory as “who can still reach what,” a lot of JS weirdness suddenly stops being weird.
The part that really clicked for me is the event listener example. That’s where most leaks actually live in real apps: not in massive computations, but in tiny, invisible references that never get severed. Closures + long-lived roots is the silent killer.
I also appreciate the emphasis on breaking references instead of “freeing memory.” That distinction matters. You’re not managing memory directly, you’re managing connectivity. The GC just follows the map you’ve drawn, even if you forgot you drew it.
This way of explaining it scales beyond JavaScript too. Once you internalize “roots → references → reachability,” you start spotting leaks in architectures, not just code. Long-lived services holding onto short-lived data is the same mistake, just at a different layer.
Really solid mental model. If more people thought about memory as relationships instead of objects, half the performance bugs I’ve seen would disappear.
Really Grate Explaination
thanks riyyan! cheers 💯✨🙏
Now I can clearly explain to someone what gc actually does! Thanks for the post
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So thoughtful. I appreciate your every post. Thanks again!
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