Watch out! This tutorial is over 6 years old. Please keep this in mind as some code snippets provided may no longer work or need modification to work on current systems.
Interpolating values is helpful if you need to pass a server-side variable to client-side JavaScript (or other languages that require it).
In the case of variables, numbers, strings, and the like, you can pass these types of variables directly into your JavaScript with bracket syntax plus an explanation point (so that the code inside the brackets is not evaluated.) This is useful for parametrizing JavaScript code that require something from your server.
