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Comment by MikeTheGreat | Hacker News Reader

I'm curious - could you expand on why it's a pitfall to think of variables as boxes?

Because that's not how variables work in JavaScript/Python etc (though it may be fine for say C++ in the case of value types and copy constructors). For example:

I'm typing on phone so for a quick example:

    let a = [];
    let b = a;
    a.push(1);

and consider the value of b now (or the fact that we could write "const" above because the binding is constant, even though we mutate the value). Or see the equivalent for Python by Ned Batchelder, which has more examples and elaboration: https://nedbatchelder.com/text/names1.html

I knew that in Python all variables are really references to objects (even when we're using a number) - is JavaScript the same way?

Also, does anyone have a link/reference to the place in the spec where it specifies this? I briefly skimmed through parts of [1] but couldn't find anything that says that JavaScript treats numbers this way.

[1] https://tc39.es/ecma262/multipage/#sec-intro

As I understand it, JavaScript does have a distinction between the primitive types and Object, but this does not show up in any significant way to the programmer / in any way relevant to how to view variables. To put it differently, the "boxes" view only applies to primitive values, while the "tentacles" view applies to all values, so the former is unnecessary and need not even be considered/taught.

I don't think there's an explicit reference in the JavaScript spec to numbers being treated this way, because this is how all variables are treated in JavaScript - the relevant part of the specification is probably the definition of the "PutValue" abstract operation[1], which doesn't include any special cases for numbers (or other primitive types) vs. objects.

[1] https://tc39.es/ecma262/multipage/ecmascript-data-types-and-...

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