Introduction

In the previous chapter, we learned how to create a Leiningen project. A project gives a structure for organizing our code. We structure our project around namespaces. We created new namespaces and we imported external Clojure libraries in order to use them in our code.

Now that you are familiar with using namespaces and creating Clojure projects, it is time to become more comfortable with working on projects that use Java and JavaScript.

As we learned in Chapter 1, Hello REPL!, Clojure compiles to Java bytecode and operates on the Java Virtual Machine (JVM). The JVM is a host platform. Any programming language that compiles to Java bytecode can run on the JVM. Because Clojure compiles to Java bytecode and runs on the JVM, we call it a hosted language. Java dates from the 1990s and is now one of the most popular backend languages. We can leverage existing Java libraries instead of writing a lot of code on our own. This helps us deliver new features faster.

As...