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The `toString()` method is JavaScript's built-in way
**to convert an object into a string** (string representation).

This method is called **automatically**,
when an object needs to be used **in a text context** -
for example, during concatenation (`+`), logging, template strings, and so on.

---

## Short version

Syntax:

```javascript
obj.toString()
```

Returns the **string representation of the object**.

---

## Example - basic behavior

```javascript
const user = { name: 'Alice' };

console.log(user.toString()); // "[object Object]"
```

By default `toString()` is inherited from `Object.prototype`,
and returns a string of the form:

```javascript
"[object ObjectType]"
```

---

## When it is called automatically

```javascript
const user = { name: 'Alice' };

console.log('User: ' + user);
// "User: [object Object]"

alert(user);
// "[object Object]"
```

JS automatically calls `toString()`
to turn the object into a string.

---

## You can override `toString()`

You can set your own string representation of the object:

```javascript
const user = {
  name: 'Alice',
  age: 25,
  toString() {
    return `${this.name} (${this.age})`;
  }
};

console.log(String(user));     // "Alice (25)"
console.log('User: ' + user); // "User: Alice (25)"
```

During `+` concatenation or `String(obj)` -
the overridden `toString()` is called.

---

## Comparison with `valueOf()`

When JS tries **to convert an object to a primitive**,
it calls, in priority order:

1. `obj[Symbol.toPrimitive]` (if present)
2. `obj.toString()` (if a string is expected)
3. `obj.valueOf()` (if a number is expected)

Example:

```javascript
const user = {
  name: 'Alice',
  valueOf() {
    return 42;
  },
  toString() {
    return 'User';
  }
};

console.log(String(user)); // "User"
console.log(Number(user)); // 42
```

---

## Different built-in objects have their own `toString()`

| Type | Example | Result |
|---|---|---|
| `Object` | `{}` | `[object Object]` |
| `Array` | `[1, 2, 3].toString()` | `"1,2,3"` |
| `Date` | `(new Date()).toString()` | `"Tue Oct 14 2025 17:00:00 GMT+0300 (...)"` |
| `Function` | `(() => {}).toString()` | `"() => {}"` |
| `RegExp` | `/abc/.toString()` | `"/abc/"` |
| `Map`, `Set` | `[object Map]`, `[object Set]` | not revealed |

---

## Advanced example - formatting JSON

If you want a string with the object's contents,
not just `[object Object]`,
use `JSON.stringify()`:

```javascript
const user = { name: 'Alice', age: 25 };
console.log(user.toString());          // "[object Object]"
console.log(JSON.stringify(user));     // '{"name":"Alice","age":25}'
```

`JSON.stringify()` is not `toString()`,
it is a separate JSON serialization mechanism.

---

## SUMMARY

| What it does | Converts an object into a string |
|---|---|
| Where it's defined | `Object.prototype.toString` |
| By default | Returns `"[object Object]"` |
| Can be overridden | Yes |
| Called automatically | during concatenation, `String()`, logs, template strings |
| Alternative | `JSON.stringify(obj)` - for full contents |

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