How to keep JavaScript function expressions in memory?

Question

let sayBye = function () {
    console.log(`Bye`);
}

let bye = sayBye;   
sayBye = null;    // X

bye();            // Y

Before asking this question, i searched in google and i found this post.

Then i thought, before line X the structure similar like this:

sayBye ---------------                                              
                      |      
                      |  => function() {....}
                      |
bye-------------------

After the x line, I thought it was like this:

sayBye                        MEMORY                                      
                            
                      |  => function() {....}
                      |
bye-------------------

But when i wrote bye in firefox developer tools i saw this

How is it possible? When i wrote let bye = sayBye; is the sayBye coppied?

let sayBye = function () {
    console.log(`Bye`);
}

let bye = sayBye;   
sayBye = null;    // X

bye();            // Y

console.log(bye);

Answer 1

From https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function/name#Inferred_function_names:

Variables and methods can infer the name of an anonymous function from its syntactic position (new in ECMAScript 2015).

Chrome and Firefox both give "sayBye" when printing bye.name.

---

From personal experiments, Chrome console shows bye.toString() when asking for bye, while Firefox shows a custom output of theirs, where they display the inferred name of the function (which makes sense indeed, as knowing the name usually helps debugging).