Suggest an edit

Improve this article

Refine the answer for “What is window?”. Your changes go to moderation before they’re published.

Approval required

Content

What you’re changing

Title (EN)

Short answer (EN)

Shown above the full answer for quick recall.

Answer (EN)

The `window` object is the **global browser object**,
which represents the **tab's window** in which JavaScript runs.

It is the **root object for the entire browser environment**,
and through it you can access all global variables, functions, and `document` itself.

---

## 1. What `window` is

`window` is an object that **describes the current browser window**
and contains:

- the **web page itself** (`document`),
- **window control methods** (opening, closing, scrolling, and so on),
- **timers** (`setTimeout`, `setInterval`),
- **browser APIs** (localStorage, history, location, and others),
- **all global variables** (for example, those declared via `var`).

---

## 2. Example:

```javascript
console.log(window.document); // access to the DOM
console.log(window.location.href); // page URL
console.log(window.innerWidth); // browser window width
```

> In practice, in the browser **almost everything "lives" inside** `window`.

---

## 3. `window` is a global object

When you write:

```javascript
alert("Hello");
```

this is the same as:

```javascript
window.alert("Hello");
```

Almost all global functions and properties actually belong to `window`.
The same applies to variables declared via `var`:

```javascript
var x = 10;
console.log(window.x); // 10
```

But - variables declared via `let` and `const` are **not added to window**:

```javascript
let y = 5;
console.log(window.y); // undefined
```

---

## 4. Main properties and objects inside `window`

| Property / Object | What it does |
|---|---|
| `window.document` | The HTML document (DOM tree) |
| `window.location` | URL information and navigation methods |
| `window.history` | Navigation history |
| `window.navigator` | Information about the browser and system |
| `window.localStorage` | Persistent data storage |
| `window.sessionStorage` | Temporary storage for the session |
| `window.console` | Access to the console (`console.log`) |
| `window.alert()`, `confirm()`, `prompt()` | Dialog windows |
| `window.setTimeout()` / `setInterval()` | Timers |
| `window.innerWidth`, `window.innerHeight` | Viewport dimensions |
| `window.scrollTo()`, `window.scrollBy()` | Page scrolling |

---

## 5. Examples:

### Navigation control:

```javascript
console.log(window.location.href); // https://example.com
window.location.href = "https://example.org"; // navigate to another site
```

---

### Timers:

```javascript
window.setTimeout(() => {
  console.log("2 seconds have passed");
}, 2000);
```

---

### Page scrolling:

```javascript
window.scrollTo({ top: 0, behavior: "smooth" });
```

---

### Storage:

```javascript
window.localStorage.setItem("theme", "dark");
console.log(window.localStorage.getItem("theme")); // "dark"
```

---

## 6. Relationship:

```javascript
window
 ├── document   -> HTML document (DOM)
 ├── location   -> URL and navigation
 ├── history    -> navigation history
 ├── navigator  -> browser information
 ├── localStorage / sessionStorage -> storage
 ├── console
 ├── timers (setTimeout, setInterval)
 └── ... and much more
```

---

## 7. Key difference from `document`:

| Property | `window` | `document` |
|---|---|---|
| What it represents | The browser tab (window) | The page content (DOM) |
| Global object | Yes | No |
| Contains | The whole environment (DOM, timers, APIs) | Only the tree of HTML elements |
| Example | `window.innerWidth` | `document.body` |

Markdown · drag & drop images · ⌘B / ⌘I shortcuts470 words

For the reviewer

Note to the moderator (optional)

Visible only to the moderator. Helps review go faster.