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## Short answer

The `=` operator **does not copy an object**,
it only **copies the reference to it in memory**.
That is, both names (variables) will **point at the same object**.

---

## Example

```javascript
const user = { name: 'Tim' };
const clone = user; // "copy" the object

clone.name = 'Oleh';

console.log(user.name);  // 'Oleh'
console.log(clone.name); // 'Oleh'
```

Changing `clone` also changed `user`,
because **it is the same object in memory**.

---

## What this looks like "under the hood"

```javascript
Memory:
┌────────────┐
│  { name: 'Tim' }  │
└──────┬─────┘
       │
       ├── user
       └── clone
```

Both `user` and `clone` are **references** to the same object.
When you write `const clone = user`, **another reference** is created, not a new copy.

---

## Why this happens

JavaScript has two data types:

| Data type | How it is copied |
|---|---|
| **Primitives** (`number`, `string`, `boolean`, `null`, `undefined`, `symbol`, `bigint`) | by value |
| **Reference types** (`object`, `array`, `function`, `Map`, `Set`, etc.) | by reference |

```javascript
let a = 5;
let b = a;
b = 10;

console.log(a); // 5 (a copy of the value)

const obj1 = { x: 1 };
const obj2 = obj1;
obj2.x = 2;

console.log(obj1.x); // 2 (a reference)
```

---

## If you actually need a copy

Use one of these approaches:

| What you need | How to do it |
|---|---|
| A shallow copy | `{ ...obj }` or `Object.assign({}, obj)` |
| A deep copy | `structuredClone(obj)` or `_.cloneDeep(obj)` |

Example:

```javascript
const user = { name: 'Tim' };
const clone = { ...user }; // creates a new object

clone.name = 'Oleh';

console.log(user.name);  // "Tim"
console.log(clone.name); // "Oleh"
```

Now the objects are **independent**.

---

## Summary

| What happens with `const b = a` | Explanation |
|---|---|
| Primitives (numbers, strings, etc.) | The **value** is copied |
| Objects, arrays, functions | The **reference** is copied, not the content |
| Changing the copy affects the original | Yes, if it is an object |
| How to avoid it | Use spread (`{ ...obj }`) or `structuredClone()` |

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