The tools we use have a massive impact on the habits we fall into when writing code. When coding, just as in life, we want to gather good habits and avoid bad habits. An example of a good habit would be writing syntactically valid JavaScript. To help us enforce this good habit, we can use a linter to inform us when our code is invalid. We should consider each tool in this way. What good habit does it inspire? What bad habit does it discourage? 

If we recall our original tenets of clean code (R.E.M.U) we can observe how various tools help us abide by them. Here's just a small collection of tools that would be of service to the four tenets:

• Reliability: Testing tools, user feedback, error loggers, analytics, linters, static typing tools, and languages
• Efficiency: Performance measurement, analytics, user feedback, UX reviews, ecological costing (for example, carbon footprint)
• Maintainability: Formatters, linters, documentation generators, automated builds, and continuous integration
• Usability: Analytics, user feedback, documentation generators, accessibility checkers, UX reviews, and hallway testing

Tools that inspire good habits work by augmenting our feedback loops. A feedback loop is whatever eventually makes you realize that you need to make a change. Perhaps you introduced a bug that caused an error to be logged. Perhaps your implementation is unclear and a colleague complained. If tools can catch these situations early, then it can speed up our feedback loop, enabling us to work faster and to a higher level of quality. In the following diagram, we illustrate Our Feedback Loop and how it is fed by information from tools at each stage of development:

Throughout our stages of development, there are many avenues of feedback. There are linters to tell us when our syntax is problematic, static type checkers to confirm we are using types correctly, and tests to confirm our expectations. Even after deployment, this feedback continues. We have error logs that indicate failure, analytics that tell us about user behavior, and feedback from end users and other individuals informing us about breakages or areas for improvement.

In this chapter, we'll be covering a small selection of the tools that can help us in building good habits and a positive feedback loop. Specifically, we're going to cover the following:

• Linters and formatters
• Static typing
• E2E testing tools
• Automated builds and CI