# Arrays

An array is a data structure that contains any number of items (or `elements`). In JavaScript, array elements can be of any data type.

Create an empty array:

```javascript
const arr = []
```

Elements in the array should be separated by commas.

```javascript
const satchel = [
  'chair',
  'table',
  'candle',
  'map',
  'magnifying glass',
  'rupees',
  'Quick Eze',
  'boomerang'
]

const squares = [1, 4, 9, 16, 25, 36, 49, 64, 81, 100]
```

#### Accessing Elements

Each element in the array has a numbered `index`. The first element has an index of `0`.

Access elements by putting the `index number` in square brackets.

```javascript
const satchel = [
  'chair',
  'table',
  'candle',
  'map',
  'magnifying glass',
  'rupees',
  'Quick Eze',
  'boomerang'
]

console.log(satchel[0]) // => 'chair'
console.log(satchel[1]) // => 'table'
```

#### Getting the Number of Elements in an Array

We can use the `.length` property to find out the number of elements in an array

```javascript
const satchel = [
  'chair',
  'table',
  'candle',
  'map',
  'magnifying glass',
  'rupees',
  'Quick Eze',
  'boomerang'
]

console.log(satchel.length) // => 8
```

#### Changing Elements

* To change an element in an array, first access the element, and then assign a new value:

```javascript
const satchel = [
  'chair',
  'table',
  'candle',
  'map',
  'magnifying glass',
  'rupees',
  'Quick Eze',
  'boomerang'
]

satchel[2] = 'glowing orb'

console.log(satchel)
```

**NOTE**: `const` only prevents reassignment, the value can still be mutated.

### Iterate over an array

Let's use a `for..of` loop to iterate over the array and print each element out.

```javascript
for (let item of satchel) {
  console.log(`A nimble rogue is trying to steal my ${item}!!!1`)
}
```


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