# Higher Order Function (HOF)

A function that takes a function as a parameter or returns a result. In other words, a higher order function takes a parameter and calls it at a necessary point, or creates a **closure**. (Java scripts can be used as value as first-class objects.)

A higher order function is oriented towards immutability and rejects mutable data that changes the external state. In other words, the pure function is a functional programming that suppresses the side effect as much as possible.

## .sort( )

#### = (!) Changes the original array (ascending order)

#### Return Value

Arrange the elements of the array properly and returns the sorted array.

## .reverse( )

#### = (!) Changes the original array (descending order)

#### Return Value

Arrange the elements of the array properly and returns the sorted array.

## .forEach( callback : ( value : T/ index : number/ array: T\[ ] ) => void)

* Use forEach instead of for syntax
* It traverses the array and executes the callback function given as an argument for each element of the array. **The return value is undefined.**

## .map( callback : ( value : T ))

## .filter( callback : ( value : T / index : number / array : Array ))

## .reduce( callback : ( ) => )

## .some( callback : ( ) => )

## .every( callback : ( ) => )

## .find( predicate : ( ) => )

## .findIndex( predicate ( ) )