Sass provides an amazing series of build in functions that are very useful in performing regular day to day functions like: darkening a color or going through a list of values. These functions are outlined in the Sass Functions API and we have also included it in the appendix of this book.
However, there are times when a custom function are needed. This is where the power of Sass and the custom function becomes very handy. In the following chapter, we will be talking about how to create a custom function and how to use it in your Sass CSS.