# Functions
Functions, are one of the most powerful and essential notions in programming.
Functions like mathematical functions perform transformations, they take input values called **arguments** and **return** an output value.
- Introduction
- Basics
- Comments
- Variables
- Types
- Equality
- Numbers
- Creation
- Basic Operators
- Advanced Operators
- Strings
- Creation
- Concatenation
- Length
- Conditional Logic
- If
- Else
- Comparators
- Concatenate
- Arrays
- Indices
- Length
- Loops
- For
- While
- Do...While
- Functions
- Declare
- Higher order
- Objects
- Creation
- Properties
- Mutable
- Reference
- Prototype
- Delete
- Enumeration
- Global footprint