Why, when assigning the value of variable "1" to variable "2", variable "2" is replaced by "1"?

Question

JavaScript

Good day, in general, I am self-taught, I am making a telegram bot on Node.JS.
I am implementing the possibility of placing an order, but in the process there was a problem that I do not understand how to solve.
You need to assign the value of the variable "1" to the variable "2". As a result, it turns out that nothing changes, and the value of the variable "2" changes to the variable "1", that is, everything happens the other way around.
I don't know how to explain it clearly, so here's how I did it:
There is an object with "sessions", when the user sends a message, the following happens:

session[ID] = session[ID] || {
    log: [PathTmpl.main_menu],
    inline_log: '',
    name: ctx.from.first_name,
    last_name: ctx.from.last_name,
    auth: 'new',
    admin: false,
    orders: [],
    phone: '',
    delivery: emptyAdress,
    order: emptyOrder
  }

Pay attention to the order and orders variables .
The emptyOrder object is a constant, with keys and empty values

const emptyOrder = {
  id: 0,
  name: '',
  pack: '',
  code: '',
  amount: '',
  price: ''
}

Orders is an array, the selected products from the order object are added to it .
As the product is selected, data is added to the order :

session[ID].order.code = code
…
session[ID].order.name = infoTxt.name
…
session[ID].order.pack = infoTxt.packing
…
session[ID].order.price = infoTxt.cost
…
session[ID].order.amount= amountNum

After that, order is pushed into the orders array and cleared, preserving the keys:

session[id].orders.push(session[id].order)
session[id].order = emptyOrder

Everything seems to be logical, but it’s worth looking at what is in the variables IMMEDIATELY after these lines
I output it to the console

console.log('\n session[id].orders : \n', session[id].orders) // массив
console.log('\n session[id].order : \n', session[id].order) // объект
console.log('\n emptyOrder : \n', emptyOrder) // константа

You can already notice that the emptyOrder variable has been replaced with the value order , but this shouldn't happen. And the order itself hasn't been cleared...
And here's what happens if you add another product:

That is, it does not add a new product to the array, but replaces all elements with the last selected product.

I don't understand what it is and how to solve it.
The same is true for shipping information. I noticed that after one user has entered the delivery address, it is added to the emptyAdress constant , and after that the next user is shown information from the same emptyAdress , that is, he sees the data of another user!
Curious if anyone else has experienced this and what are the possible solutions?

Answer 1

You are not assigning a value, but a reference to a value. This is the case with objects and arrays.

let a = {x:1};
let b = a; // Теперь a и b указывают на один и тот же участок памяти.
b.x = 2;
console.log(a.x); // 2    Ах, вот оно как!

//Как скопировать:
let c = {}; //Создается новый объект и под него выделяется новая память
c.x = a.x; //Копирование значений, т.к. x это не объект.

//Универсальный вариант (копируются все свойства):
a.y = 11;
a.z = 111;
let d = Object.assign({}, a); 
console.log(d); // {x:1, y:11, z:111}

Object.assign()

Answer 2

When you assign an object, you are assigning a reference to the object, not making a copy of it. And then you overwrite the fields of the emptyOrder itself, through a link to emptyOrder in session[ID].order. Need to make a copy of the data...
session[ID] = session[ID] || {
log: [PathTmpl.main_menu],
inline_log: '',
name: ctx.from.first_name,
last_name: ctx.from.last_name,
auth: 'new',
admin: false,
orders: [],
phone: '',
delivery: emptyAdress,
order: Object.assign({}, emptyOrder)
}
PS Don't forget to include a polyfill for Object.assign or use a similar framework method.