astexplorer VS ESLint

You can play with your code here, and visualise ASTs for the same.

Website

To understand this syntax, I recommend exploring AST Explorer. You will have a better view of how the AST of JavaScript works and how to correlate it with the Eslint syntaxy:

You can never mistake type_declaration with an identifier, otherwise the program will not work. Aside from that constraint, you are free to name them whatever you like, there is no one standard, and each parser has it own naming conventions, unless you are planning to use something like LLVM. If you are interested, you can see examples of naming in different language parsers in the AST Explorer.

The rule that I want to write will be called not-allows-underscore: the idea is to abolish the use of underscores when declaring variables or functions. It's a real dummy rule, but it should be enough to see in action the concepts that we have discussed earlier. The first thing that I would do is to go to AST Explorer, write down a code that declares variables and functions (both standard and arrows one) and take a look at what type of node is the one that encodes the identifier. Doing that, I found out that the node type of my interest is Identifier, what a surprise! 🤣. In particular, the structure of the node holds the string used as identifier in the name property.

All the information about the API, AST node names, AST Explorer, etc. you can read in the official documentation. I’m just going to show examples of how to automate the check-up of our created conventions.

AST Viewer

If you want to see how the AST of popular languages looks, I recommend the AST Explorer. It supports various languages, and you can view the complete AST and navigate through the nodes. If you want to go further, you can try to copy some logic from an existing parser and implement it in your own, such as calculating an expression according to precedence order, for example: 1 + 2 * 3 (which is 7, not 9).

https://astexplorer.net/ is a good resource/playground for understanding ASTs and transpilers.

Let's be honest - setting up tools for a new project can be a frustrating process. Especially when you want to jump straight to coding part. This is often the case with ESLint and Prettier, two popular tools in the JavaScript ecosystem that can sometimes interfere with each other when it comes to code formatting. Fortunately, there's a simple solution to this process, and it's called eslint-plugin-prettier.

Do you have the need to find and fix problems in your JavaScript? Then ESLint is for you. With over 120 million downloads each month, it's definitely one of the most popular projects out there. The latest version introduces a new configuration system, designed to simplify available configuration options. Old and deprecated rules have been removed, and a new configuration inspector has been added. Check out the blog for all the highlights, and a migration guide.

ESLint: A pluggable and configurable linter tool for identifying and reporting on patterns in JavaScript.

Automating code checks with static code analysis allows us to enforce code styling effectively. By integrating tools into our workflow, we can identify errors at an early stage, while coding instead of blocking us at the end. For instance, flake8 checks Python code for style and errors, eslint performs similar checks for JavaScript, and prettier automatically formats code to maintain consistency.

If you're a developer, you're surely familiar with Prettier and ESLint. With over 8 years of existence, they have established themselves as references in the JavaScript ecosystem.

eslint is used to avoid code errors

No lint errors: The committed code does not contain any lint errors (eslint).

Let’s walk through the steps for a one-time setup to configure husky pre-commit and pre-push hooks, ESLint with code styles conventions, prettier code formatter, and lint-staged. Husky automatically runs a script on each commit or push. This is useful for linting files to enforce code styles that keeps the entire code base following conventions.

GitHub | Website

ESLint: A pluggable and configurable linter tool for identifying and reporting on patterns in JavaScript.