Writing code is a creative process. Programmers will be quick to differ in opinion on whether the solution to a problem should be implemented in one way or another — citing tradeoffs in algorithms, structures, or even languages. Due to these trade-offs, the problems programmers face most frequently will have several different solutions, all correct but all written differently with various factors considered. Because “correct” code can take so many different forms, developers have cultural notions of code quality that is somewhat independent of these decisions.

One concept that is central to the notion of quality code is that all code is read many, many more times than it is written. Maintaining and updating code takes up much more of a software developer’s time than production. There are many ways to make this less of a burden, and these techniques frequently correspond to code quality principles. Naming variables consistently so that they’re identifiable is one way to improve the readability of a codebase. Another pillar of code quality is avoiding duplication of code within a codebase.

Code duplication is an invitation for bugs. If incorrect code is copy-and-pasted in multiple places, a developer might remedy the flaws in only a few of those places and fail to fix the buggy code everywhere. In this course, we will investigate several ways to avoid replication and reduce complexity. In programming in general, this often means putting the reused code into reusable containers like functions and objects. In Express specifically, this will also mean composing our desired functionality into a series of middleware functions.