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## 1. `for`: the classic loop

> Used when **the number of iterations is known in advance**.

```javascript
for (let i = 0; i < 5; i++) {
  console.log(i);
}
```

Result:

```javascript
0
1
2
3
4
```

Structure:

```javascript
for (initialization; condition; step) {
  // loop body
}
```

- `initialization` runs once at the start
- `condition` is checked before every iteration
- `step` runs after every iteration

---

## 2. `while`: a pre-condition loop

> Runs **while the condition is true**.

```javascript
let i = 0;

while (i < 5) {
  console.log(i);
  i++;
}
```

Used when the number of iterations is **not known in advance**.

---

## 3. `do...while`: a post-condition loop

> Guaranteed to run **at least once**.

```javascript
let i = 5;

do {
  console.log(i);
  i++;
} while (i < 5);
```

Result:

```javascript
5
```

> The loop body runs first,
> then the condition is checked.

---

## 4. `for...in`: iterating over **an object's keys**

> Used to walk through **an object's properties**.

```javascript
const user = { name: 'Oleh', age: 25, city: 'Kyiv' };

for (let key in user) {
  console.log(key, ':', user[key]);
}
```

Result:

```javascript
name : Oleh
age : 25
city : Kyiv
```

Features:

- It iterates over **all enumerable properties**, including inherited ones.
- It does not guarantee order.
- It is better **not to use it for arrays**.

---

## 5. `for...of`: iterating over **iterable objects**

> Ideal for **arrays, strings, Set, Map, and so on**.

```javascript
const numbers = [10, 20, 30];

for (let num of numbers) {
  console.log(num);
}
```

Result:

```javascript
10
20
30
```

It also works with a string:

```javascript
for (let char of 'JS') {
  console.log(char);
}
```

> It iterates over values, not keys (unlike `for...in`).

---

## 6. `forEach()`: an array method

> Not an operator, but an **array method**,
> though it does the same job: iteration.

```javascript
const arr = ['a', 'b', 'c'];

arr.forEach((value, index) => {
  console.log(index, value);
});
```

Result:

```javascript
0 a
1 b
2 c
```

Features:

- You cannot use `break` or `continue`.
- It is convenient for **iterations without an early exit**.

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