# Arrays

## Array

It is just an `object` that offers operations to access and manipulate its properties.

`arr.length`: Shows the number of elements inside the Array, but it also considers empty positions.

* Then, it would show a wrong number of `used` positions.
* Thus, avoid using `delete` to remove elemnts from the `Array`.

**Mutator methods**

They modify the `Array`.

`arr.push(el)`: Add element to the end.

`arr.pop()`: Remove element from the end.

* \[Also returns the removed element]

`arr.unshift(el)`: Add element at the beginning.

`arr.shift()`: Remove element at the beginning.

* \[Also returns the removed element]

`arr.splice()`: Removes, substitutes ou add, one or more elements in a specifig position.

* \[Also return the removed elements]

`arr.sort(fn)`: Sorts the elements according to a `function`.

* \[-1 and 0 the element stays where it is; 1 it inverts with the other one]
* \[It changes the `Array` in place, does not return a new one]

`arr.reverse()`: Reverse the elements order.

`arr.fill()`: Fills (all or specific interval) of the values with the specified value.

**Array iteration**

They iterate over `Array` values.

`arr.forEach(fn)`: Execute the given `function` for each element.

`arr.filter(fn)`: Returns a `new` array with only the filtered elements.

`arr.find(fn)`: Returns the `first` element that returned true in the given `function`.

`arr.some(fn)`: Returns true if one or more elements returned true in the given `function`.

`arr.every(fn)`: Returns true if all the elements returned true in the given `function`.

`arr.map(fn)`: Returns a `new` array based on the return of the given `function.`

`arr.reduce(fn(result, current) => {})`: Return a value based on the return of the given `function.`

**Accessor methods**

They return specific information about the `Array`.

`arr.indexOf()`: Returns the position of the first found element.

`arr.lastIndexOf()`: Returns the position of the last found element.

`arr.includes()`: Return true if the given element exists.

`arr.concat()`: Returns a `new` array result of the concatenation.

`arr.slice()`: Returns part of an array, given a \[start, end) position.

`arr.join()`: Converts the array to a string, joining the elements with a given separator.