Deciphering Javascript Checkers: Know Why and When You Might Use Them

We’re all familiar with rules of grammar, which aid in communication by letting us know when to use a comma, how to spell a word or the proper use of prepositions.

Tools such as Grammarly allow you to run text through a checker to ensure you’re following those rules and make suggestions to improve the writing overall.

There are also checkers out there to help with improving code quality, similar to the way Grammarly improves writing quality. In this article, we will go over JavaScript checkers, as JavaScript was the most popular language in 2020, according to GitHub. JavaScript checkers, or linters, are great tools for making sure your entire team is writing high-quality code and following the same rules across the board.

Let’s take a look at what these tools are, why you want to use them, and how to best take advantage of them. 

Static Code Analysis

When you have a large project, you need programmatic tools to validate the correctness and ensure code quality. The idea is to check the code and predict but also find actual issues in it without actually running or compiling the code.

With JavaScript code, the tools used to perform a static analysis fall into the categories of formatters and linters.

Formatters do pretty much as the name implies. They check your code for consistency in how it is formatted — like whether you used tabs or a specific number of spaces, what type of string delimiters are used, and even line widths. 

A linter can handle formatting checks, but also scan source code for more complex issues. They use a set of rules to find any predefined issues to watch out for. Many of these rules are generic, but you can define specific rules for your project.

Linting tools can help in several aspects; besides flagging issues and providing warnings, they also provide suggestions for best practices consistent with the programming language being used. They not only flag style issues, programming errors and bugs, but also more serious issues, like security vulnerabilities. 

Linters, also called static analyzers, perform static code analysis by providing alerts and finding the above errors and issues, before the code is compiled and actually runs. They help automate the code review process: they not only enable developers to find bugs much earlier and keep a consistent code style, but more importantly, they boost productivity; with linters in place, it helps save time in code reviews and you can spend more time developing products, or fixing other bugs. 

JavaScript Checking Tools

A JavaScript checker is a kind of code review tool meant to automate the review process. Tools come in all types and for all languages. We’ve integrated Codacy to work with several of them, for the 36 programming languages currently supported, including a few specifically for JavaScript. For static analysis, it includes ESLint, JSHint, and PMD. JavaScript checkers catch problems you might miss when trying to review lines and lines of code.

Potential Uses of JavaScript Checkers

JavaScript checkers provide several different functions. A specific tool might offer one or all of the following use cases. 

Code Checking

Code checking entails scanning source code and looking for potential problems. This could be anything from breaking a naming convention or unused code to potential issues in performance and complexity.

The main goal is checking to see that your code follows the specific coding standards you have set up. Your team might follow a common convention such as Google’s style guide, or you might have your own in-house rules to guide you. A good tool should be fully configurable to follow whichever style you prefer.

Code uniformity means all your developers name the classes and properties the same way based on the standards you develop. The more people and the larger the project, the more essential it is to keep a handle on this.

Documentation Enforcement

Along with your code standards, inline documentation plays a key role in making sure everyone stays on the same page. This is especially true for developers joining a new team. Your checker can ensure that there are comments documenting your code so that it is easier for everyone to adhere to your standards. It is also important for adding and keeping track of TODOs and FIXMEs. 

Bug Finding

JavaScript error checkers also look for general bugs in the code, comparing what you’ve written against common bug patterns. These can cover correctness, malicious code, performance, and security, among others. Security is an ongoing problem for JavaScript so a tool with additional checks for common vulnerabilities, such as types of injection and sensitive data exposure is important to have.

When Do You Check Code?

With a language like JavaScript, you actually have a choice as to when and how to check the code. Most developers will run a static analysis on their own machine before sending off changes. 

Your first time to do a code check might be in your own local environment before you submit the code to a shared repository such as GitHub, even though the checks done locally can be exactly the same as the ones done on the continuous integration server. 

A later check might also be done manually by fellow developers during a regular code review process. The goal is to get the code as consistent, maintainable, and correct as possible before it hits the production server. 

Deploy Your JavaScript Checkers

There are many tools used in code analysis, and we recommend you check out the array of JavaScript checkers if you care about code quality and consistent standards, and want to automate the code review process. 

At Codacy, we integrate some JavaScript checkers, including ESLint, JSHint, and PMD. Codacy analyses commits for you automatically, giving you details on any problems found, how to solve them, and also provides an estimate of how long it will take to solve the issues. This also aids in tackling technical debt, which is a well-known term in software development. Automated code review can save up to 50 percent of time spent doing code reviews and ship features faster. This is an impressive statistic, and it can be something remarkable for any team and overburdened developer, as the pressure to deliver well-built products and new releases with high quality fast and safely is more important than ever. 

Check out the rest of our blog for more tips on how to improve code quality.