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`Object.keys()` is a built-in JavaScript method
that **returns an array of all** ***own*** **(non-inherited) property names** of an object as strings.

---

### Syntax

```javascript
Object.keys(obj)
```

- `obj` - the object to get the list of keys from.
- Returns an **array of strings**.

---

### Example

```javascript
const user = {
  name: 'Tim',
  age: 25,
  city: 'Berlin'
};

console.log(Object.keys(user));
// ['name', 'age', 'city']
```

All of the object's keys (own, enumerable) are returned in the array.

---

### Features

1. **Returns only "own" properties**
(not ones inherited via `prototype`):

```javascript
  const person = { species: 'human' };
  const user = Object.create(person);
  user.name = 'Tim';

console.log(Object.keys(user)); // ['name']
  ```
2. **Order of keys**
Matches the order they were added to the object (for regular properties).
3. **Works only with enumerable properties**
(if a property was created with `enumerable: false`, it will not appear in the list).

---

### Example with an empty object

```javascript
console.log(Object.keys({})); // []
```

---

### Often used together with other methods

#### Get the list of values:

```javascript
Object.values(user); // ['Tim', 25, 'Berlin']
```

#### Get an array of key-value pairs:

```javascript
Object.entries(user);
// [['name', 'Tim'], ['age', 25], ['city', 'Berlin']]
```

#### Iterate with `forEach`:

```javascript
Object.keys(user).forEach(key => {
  console.log(`${key}: ${user[key]}`);
});
```

Output:

```javascript
name: Tim
age: 25
city: Berlin
```

---

### Summary

| What it does | Returns | Accounts for the prototype | Data type |
|---|---|---|---|
| List of an object's **keys** | Array of strings | No | `Array` |

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