Node JS is one of the popular frameworks for web development. It has been used by several companies, ranging from small projects to large solutions. With it, you can create lightweight, scalable, fast, and robust server-side web applications by writing maintainable JavaScript code for the browser.

Today we're going to talk about some best practices to write maintainable Javascript code in Node JS that will help all types of developers build an efficient and more maintainable application. The topics are:

1. Good understanding of JavaScript and Frameworks
2. Use Typescript
3. Replace Callbacks with Async
4. Code formatting and style
5. Add comments in code and documentation:
6. Writing meaningful test cases

Good Understanding of JavaScript and Frameworks

JavaScript is a curious language. It is easy to write. And more than 95% of the internet uses JavaScript on their websites to become browser language. It offers much more functionalities nowadays than just primitive data structure and unreliable browser APIs.

To become a master in JavaScript, you need to understand a core feature in JavaScript, such as asynchronous JavaScript, generator functions, scoping, performance, etc.

Here are some points, which help you to be good at JavaScript:

1. Test code performance: Test your code with profilers, debuggers, and time measurements. Test the worst-case scenario to see if your code is a performance bottleneck. For example, if we are using forEach loop rather than for-loop, it may come up with heavy computational operations or asynchronous JavaScript with big datasets.
2. Do not depend on NPM for everything: Most of the simplest libraries are easy to implement by yourself. It will save your project from having a regular updates of packages and test compatibility.
3. Analyse your bundle size impact: You don't need to load the whole Lodash library for a single _.omit call. Loading a huge bundle slows your app's initial loading time.

Use TypeScript

TypeScript extends JavaScript and improves the developer experience. It enables developers to add a type of safety to their projects.

It provides various other features like interfaces, type aliases, abstract classes, function overloading, etc.

Consider seeing these examples without any context:

The problem which this approach is,

What does getPicture return, what if you want to add a function to create a post – how do you define the structure of data in an object? Now take a look at,

The key difference is transparency. Now you can understand the code and your IDE or tsc will assist you with it. When you call the TS version of getPicture, you will get useful information now.

Replace Callbacks with Async

In the beginning, callbacks were used to create asynchronous methods in Node JS, but when nested continuously, they tended to get out of control.

It is at this point that the code becomes unreadable. With the introduction of async/await, developers have noticed a lessening of this problem. You can easily avoid this bad callback scenario by replacing it with async and await calls.

Code Formatting and Style

This is a very important aspect of development. Regardless of working individually or in a team, it always helps to enforce some rules.

1. Use ESLint and Prettier: If we use both, you can focus on what your code does. Imagine never again failing an automated test because of a missing trailing comma. By using prettier by defaults, you can end code-style arguments once and for all.
2. Use descriptive naming for variables: You need to understand what these variables or functions will do, consider these variables, for example, buttonDomElem vs btnDomEl or loading vs isUserDataLoading, which is easier to understand. Prefix boolean variables with a verb like is or has and don’t be afraid of longer variable names.

Add Comments in Code and Documentation

When you write complex parts of code, always aim to write your code for other developers who can easily understand it. There are some sets of libraries that will generate code documentation from the inline comments you mentioned during development.

Use JSdoc in your project, it is very helpful because it will generate documents based on the methods and parameters we are using in our project. All we need to do is, write an inline comment in whatever places we need. The JSDoc will automatically take that as a keyword and generate a new API document for us.

Writing Meaningful Test Cases

When you are developing a crucial backend feature based on thorough specification, you will benefit from test driven development. But if you are creating a front-end dashboard app, using TDD can slow you down dramatically. Consider these points,

1. Unit Testing: It is the go-to testing method for most use cases. Unit testing your frontend app can evaluate complex components like layouts, modal dialogues, wizards, multi-step client-side validated forms, etc. In backend development, you can verify whether the endpoints handle good and bad cases the way you expect them to.
2. End-to-End Testing: End-to-end testing is a process in which the entire lifecycle of an application is tested from a user’s perspective in a production-like scenario. In Node JS development, you can use a combination of Chrome API Puppeteer and the JavaScript testing framework Jest to automate e2e testing. This allows you to ensure that the UI of your application is still functioning as you fix bugs and add new features.

Conclusion

As a developer, it is very important to learn and be aware of best practices that save your time, enhance your skills and help you write understandable code. From this blog, you must have now learnt about the importance of maintainable JavaScript and frameworks, when and how to use typescript, the use of callbacks, and the importance of formatting the code. Another very important aspect that makes your code more relevant is the wise and timely use of comments in code and documentation. This way it makes a code favourable for other developers as well to maintain and update it in the future. Lastly, the importance of test cases.