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Is everything in JavaScript an Object?

mayankav on July 10, 2021

Well well! The motivation for this post comes from my last post where I had a comment from one of my readers that I couldn't agree with. I was talk...

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Calin Baenen • Jul 11 '21 • Edited

~~Jokes on you, since everything except numbers and arrays are objects in every language! >:)~~

~~(I don't mean Object object, I mean "object" as in a container, like the result of a constructed struct, union, or class.)~~

~~(This was only partially relevant.)~~

Calin Baenen • Jul 11 '21 • Edited

To explain how I think about an object, this is what I think of an object as:

type Person struct {
  name [2]string;
  age float32;
} // "Person" type.

p := Person {name: {"Calin", "Baenen"}, age: 14.8333}; // Person object.

mayankav • Jul 11 '21

@baenencalin Didn't get you man! In JavaScript, arrays infact are objects :)

Calin Baenen • Jul 11 '21

To add clarity, strings are a little in the gray area.
If you're using a language like Go, if we disregard the built-in string type, they may be an array, or they may be a struct type, or they may be a wrapper type for an array, which would be an array of numbers, say int16 or int32.

Of course, to be fair, we should consider the built in type - though, how it's built is dependent on the language.
In Java, it's definitely an object, both in the Object sense, and the sense that they are the result of a data structure.

Calin Baenen • Jul 11 '21

What I'm saying in most languages, like C, Go, C++, etc..
Everything except arrays and numbers are objects.

(I guess this isn't necessarily true for JS.)

mayankav • Jul 13 '21

@baenencalin Hey man! I get you now. I am not sure about all the other languages but what I can say is that its indeed a choice made by the langauge itself. I mean how a langauge defines primitives and objects is completely upto the language. We do have an article of faith on the universal notion though.

Calin Baenen • Jul 14 '21

I thought primitives did have a definite definition ("The least abstract(ed) type in a given language. - Usually that who's implementation is the most bare-bones (compared to other types) when looking at the source code for a given language.")?

Reardon85 • Mar 8 '23

How is a "char" in C an object? And how is a string an object but an array isn't an object?

Calin Baenen • Mar 9 '23

This is an outdated view. I realized not every language is quite like how I described.
Anyway, I never claimed chars were an object (even if they weren't listed as one ov the things that isn't an object); on the note ov arrays and strings, however, I don't consider arrays an object because they're usually just a consecutive arrangement ov data (in C it's literally just a pointer to said arrangement).

I hope this answered your questions thoroughly; feel free to write back if you have any more questions.

peerreynders • Jul 11 '21

If you assign some property to a string primitive with an intention of getting the value back at some point, you will only be returned undefined because the temporary String Object was discarded then and there.

MDN: primitive values:

All types except objects define immutable values (that is, values which can't be changed).

seems like a more straightforward explanation - i.e. nothing was changed in the first place - JavaScript just ignores the attempt of mutation.

mayankav • Jul 11 '21 • Edited

@peerreynders Indeed. Thanks for taking out time to read :)

Lilit Karapetyan • Jul 11 '21

Thank you for bringing up this topic. I heard that phrase so much that it was confusing me at the beginning of my career.
I think this myth was created by the people working in other languages who started to get acquainted with JS just a little bit :)
I don't think it is even possible for the language to only have objects as its type (Correct me if I'm wrong).
The most important note here was about the optimization part. Please, please, do not try to do these kinds of micro-optimizations yourself :) The browser engines are designed to detect and optimize all the "normal" code flows. If you try to do some weird things, the browser engine will not detect recognizable patterns and will fail to optimize the performance.

mayankav • Jul 13 '21

@lilithkarapetyan Hello Lilit! To answer your question, I'd say it completely depends on how a particular language defines primitives and objects. In JS, objects are nothing more than collective key:value pairs and anything that is not an object is a primitive. Consider another language, maybe 'C', it maps primitive types much closer to the underlying microprocessor architecture (int, char etc..). Generally in computer science "primitives" emply atomic types but then every programming language can freely decide on how to implement their own basic building block. For example Python chose to keep objects at the atomic level. So yeah, it depends on the language.

frontwebdev • Dec 14 '23 • Edited

. It is important not to confuse a primitive itself with a variable assigned a primitive value. The variable may be reassigned to a new value, but the existing value can not be changed in the ways that objects, arrays, and functions can be altered. (from mdn)

and you confused it.
when you write let str = 'hello' str is not primitive.
now try Object.isExtensible(str) you will get false and that a reason why you cannot add new prop to variable str.

Ahmed Murtaza • Jul 11 '21

Well explained!

mayankav • Jul 11 '21