First off, we're going to talk about how to write mixins: the syntax that they use, and what it does. Also, since we've already covered logical operations in templates, we can use those in mixins throughout the examples.
Mixin definitions don't output any HTML and are defined using the following syntax:
mixin book(name, price)
li #{name} for #{price} €In the preceding code snippet, book is the name of the mixin, and name and price are both named arguments. The indented block of Jade gets executed in its own scope, where the variables name and price are both defined with the arguments that are passed. So basically, it works just like you would expect a function to work.