Best Ways to Debug JavaScript

What are Some of the Best Ways to Debug JavaScript?

JavaScript as a programming language has exploded in popularity. Websites and web apps rely more and more on JavaScript, and it’s capabilities have grown significantly. With more JavaScript frameworks becoming the default for building web apps, the likelihood of problems and buggy JavaScript code increases. Compounding the growth of issues is that JavaScript in the front-end is notoriously difficult to reproduce, debug, and fix. 

Best ways to debug server-side javascript. 

Before we get to debugging JavaScript in the front-end, it’s important to surface some ways to debug server-side JavaScript, primarily in Node.js. Node itself conveniently ships with a number of features to help debug server-side JS. Simply enabling the --inspect flag allows you to debug node scripts and code.  In addition, using server side log aggregation tools or building your own can make the debugging process easier, as you have access to everything you need in one place. 

Best ways to debug client-side JavaScript

Debugging front-end JavaScript code brings with it some unique challenges; primarily the difficulty in identifying errors, reproducing errors, and validating that a fix actually took. 

Exposing errors:

The first step in debugging JavaScript is to proactively attempt to expose issues to the browser. While a browser will automatically capture javascript errors, warnings, and other issues, you can also use the built-in methods to help you when there might be something going wrong. Here are the options:

• console.log() - write any message or piece of information to the console
• console.debug() - very similar to console.log, but is used for browser compatibility and by default .debug messages are hidden in some browsers.
• console.warn - has a different type of output message, and is typically used for less-critical pieces of information.
• console.info() - almost identical to console.log()
• console.error() - should be reserved for more serious issues and actual errors. This method is what automatically captures exceptions and other JavaScript issues. 

Using a combination of these methods can help you identify where in your codebase there is an issue and give some clues into what went wrong. With that information you can attempt to reproduce. 

Reproducing issues to debug JavaScript:

Once there is a known or inferred issue to debug, being able to reproduce the issue is critical in order to fix it. Much of the time, there is little information known besides an error message or console log. After asking a user for their browser / operating system or finding it in analytics, typically reproducing the error can be accomplished with using virtual machines to recreate the browser and operating system environment. In addition, there are tools like Browserstack which make this even easier. 

Debugging and fixing the code itself:

Once the issue has been reproduced and the problematic code has been identified comes actually fixing the code. Sometimes debugging is as easy as discovering a simple mistake like a typo or bad syntax. Tools like JSLint or JSHint are a quick and easy way to find common issues. Also, adding useful comments to the code can help yourself and others debug it more quickly. 

Streamline your JavaScript debugging process:

After a brief overview of some methods for debugging JavaScript, you might be thinking “there’s got to be an easier way”. You’re right. Tools like LogRocket simplify the entire JavaScript debugging process by showing you exactly what a user did that led to an issue, what the user’s environment was, and removes the need to reproduce the error. Get a free trial today.