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JavaScript has **8 basic data types**.
They are split into **primitive** and **reference (object)** types.

---

## 1. Primitive types (7 total)

A primitive is a value that **is not an object** and **has no methods**.
They are stored **by value**, not by reference.

---

### **Number**

**Numbers** - both integers and floating-point.

```javascript
let a = 42;
let b = 3.14;
```

Notes:

- Special values exist: `Infinity`, `-Infinity`, `NaN` (Not-a-Number).
- All numbers in JS are **64-bit floating-point numbers (IEEE 754)**.

---

### **BigInt**

Used for **very large integers** that exceed the limits of `Number`.

```javascript
let big = 123456789012345678901234567890n;
```

> Adds the `n` suffix.
> Lets you work precisely with integers of any length.

---

### **String**

Text strings in quotes: `'single'`, `"double"`, or `template` quotes.

```javascript
let name = "Tim";
let message = `Hello, ${name}!`;
```

> Strings are **immutable** - a new string is created on any change.

---

### **Boolean**

Logical values - `true` or `false`.

```javascript
let isAdmin = true;
let isLoggedIn = false;
```

> Used in conditions, checks, and logical expressions.

---

### **Null**

A special value denoting **"nothing"** or **"empty"**.

```javascript
let user = null;
```

> Its type is **object** (a historical mistake in JavaScript that stuck).

---

### **Undefined**

A variable **declared but with no assigned value**.

```javascript
let x;
console.log(x); // undefined
```

> Assigned automatically when no value is set.

---

### **Symbol**

A unique, immutable value often used as an **object key**.

```javascript
let id = Symbol('id');
let obj = { [id]: 123 };
```

> Every Symbol is unique, even with the same description.

---

## 2. Reference type

### **Object**

Stores **collections of data and functions**.
Passed **by reference**, not by value.

```javascript
let user = { name: "Tim", age: 25 };
let arr = [1, 2, 3];
let func = function() {};
```

Object subtypes:

- `Object` - the base type.
- `Array` - an array.
- `Function` - a function.
- `Date`, `RegExp`, `Map`, `Set`, and so on.

| Data type | Example | Description |
|---|---|---|
| **Number** | `42`, `3.14`, `NaN` | Numbers |
| **BigInt** | `123n` | Large integers |
| **String** | `'Hello'`, `Hi ${name}` | Strings |
| **Boolean** | `true`, `false` | Logical type |
| **Null** | `null` | Absence of value |
| **Undefined** | `undefined` | Not defined |
| **Symbol** | `Symbol('id')` | Unique identifier |
| **Object** | `{}`, `[]`, `function(){}` | Collections and structures |

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