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Comment by bryancoxwell | Hacker News Reader

Pointers in JavaScript? I’m far from a JS expert, but didn’t think the language had pointers. Could you explain what you mean here?

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I'm not aware of any mainstream language that doesn't have pointers, the question is whether they expose pointers as a first-class language construct (i.e. you can choose to not dereference them or to do pointer arithmetic) or use them as an implementation detail.

In JavaScript's case it's an implementation detail, but one that is extremely relevant when maintaining something in production.

Correction about JavaScript: All non-primitive data types are pass by reference. So not just implementation detail as no valid js interpreter will pass those by value.

It's not up to the implementation to decide whether to pass by reference or not, but it is up to the implementation whether to use pointers under the hood to model passing by reference. Since there's no pointer arithmetic, other models could theoretically be used to accomplish the same semantics [0], it just happens to be that pointers are by far the most logical choice.

[0] As a silly example: a JavaScript implementation could technically store object references as a URL of an API that allows interacting with the object, as long as this is transparent to the user and the program behaves the same as a pointer implementation (minus non-functional characteristics like performance).

Makes sense, thanks!

Most variables on JavaScript are (essentially) pointers. A common mistake people make in the language is keeping references to objects in a global map, which prevents them from being garbage collected (often a bad caching implementation).

You can use things like WeakMap or WeakRef as one solution, but there are usually better options

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