# Unit 4: Functions

- [Functional Programming](/unit-4/functional-programming.md)
- [User Defined Functions](/unit-4/user-defined-functions.md): Writing your own functions gives the ability to reuse code.
- [Hoisting and Scope](/unit-4/user-defined-functions/notes.md)
- [Calling a JS Function](/unit-4/calling-a-js-function.md): Interaction between HTML and Javascript requires a function to be called.