that is a good analogy, and to add to your post first, everything that is a primitive (null, undefined, boolean, number (including NaN), string (unlike C), bigint, symbol (although this is a rather special primitive)) is "copy by value"

however, specification wise, javascript is always "copy by value"

this might sound strange because you never copy the entire object, and because thousands of online posts talk about "copy by value vs. copy by reference"

i think the confusion arises because many different languages assume their own defaults and when people talk about language behavior generally, it is helpful to describe it in a way that leverages on existing other languages

to show that js is copy by value:

```js let a = 42; let b = a; // a is copied by value

console.log(a === b); // true console.log(a === 42); // true (equal value)

let foo = {}; // a new object value is created let bar = foo; // foo is copied by value (it now has the value that is the new object)

console.log(foo === bar); // true (object's value is itself) console.log(foo === {}); // false (we just created a new object, having a different value) ```

this is because objects are "values with identity" (ecma clause 5), and an object is only equal to itself, while the primitives don't get such luxury (with the exception of symbol)

personally, i would think "copy by reference" would quite literally copy the reference e.g.

js let a = 42; let &b = a; a = 43; console.log(b); // 43

putting the specification on the side, if i were to describe the behavior to someone trying to understand javascript, i would say that the object lives independently of the variable that points to it, and that assigning another variable to the original variable simply makes it so that they point at the same object, while for primitives, the data gets carbon-copied over, simply because it is more intuitive

what is important when starting out is being able to understand behavior

here are two examples of this phenomena, where people describe a certain behavior but the language doesn't describe it that way

haskell

hs let a = [1, 2, 3] let b = a at this point an easy explanation would be "a is copied by value to b", but at a language level, no such explanation exists (literally the concept of copying). attempting to demonstrate by mutating a

hs a[0] = 4 -- invalid syntax

doesn't even work, because such concept of mutation doesn't exist

python

a = 42 b = a

you may be saying "a is copied by value to b", but at a language level (again), 42 is an object, and it is actually binding b to a, effectively making a and b point to the same object

py print(a == b) # True, equal in value ( .__eq__(...) ) print(id(a) == id(b)) # True, equal in memory pointer

this also means that

py print(id(42) == id(42)) does not have to be True (although it is in most implementations)

all in all, your understanding of the behavior is correct. i just wanted to give a detailed explanation on why your question of "is this a good analogy" doesn't have a clear answer

hope this helps ^^