Picture this: your team just released a shiny new application. The marketing team runs a campaign, and traffic spikes. Suddenly, users start tripping over bugs and error pages. One user leaves a one-star review, and the marketing team scrambles to discover what went wrong. Sound familiar? If you've ever been in this situation, you know how stressful it can be. For businesses that rely on web applications, monitoring JavaScript errors and tracking performance with front end monitoring tools is crucial to preventing this type of scenario. This blog will help you find the best tools and services for monitoring and tracking JavaScript errors on front end applications so you can avoid user crises and maintain a good reputation.
Frontend monitoring tools like Alerty's solution for tracking JavaScript errors provide valuable insights to help you achieve your objectives. With Alerty, you can quickly understand what went wrong and how to fix it.
As of 14 June 2024, nearly 98.8% of websites use JavaScript. A 2023 stack overflow survey states that JavaScript is the most popular client-side programming language on the Internet.
The survey's findings indicate that 63.61% of developers prefer using this language. Although developers love this language, it isn't prone to errors, which are statements that prevent the program from running properly.
Error monitoring and reporting are very beneficial when diagnosing client-side browser errors. If an error occurs on a client’s browser, then error reporting can help us understand what occurred and how to fix it.
JavaScript error monitoring is the process of tracking, identifying, and managing errors that occur in JavaScript code running on a web application. This is crucial because JavaScript is responsible for many modern web applications' interactive behavior and functionality. Errors can:
What JavaScript Error Monitoring Entails:
Error monitoring tools detect and log errors as they happen in real-time. This means that when a user encounters an issue, it’s recorded and reported to your monitoring system. This allows developers to respond quickly to problems before many users are affected.
When an error occurs, it’s captured and logged with detailed information, including the error message, stack trace, browser type, operating system, and sometimes even the specific user action that triggered the error. This data is invaluable for diagnosing and fixing problems.
JavaScript is often minified in production to improve load times, making error messages challenging to decipher.
Source maps help by mapping the minified code back to the source code, making it easier for developers to understand where and why an error occurred.
Some monitoring tools offer user session tracking, allowing developers to see the events that led to an error.
This can include:
Not all errors are equally important, and some might be unrelated to your code, such as errors caused by browser extensions or bots.
Error monitoring tools often include features to filter out these irrelevant errors, helping you focus on the issues that truly impact your users.
In large applications, hundreds or even thousands of errors can be reported. Monitoring tools typically offer ways to prioritize these errors based on their severity, the number of users affected, or the frequency of occurrence. This helps teams focus on fixing the most critical issues first.
Error monitoring systems can be configured to send alerts when certain errors occur or when an error affects many users. This ensures that critical issues are brought to the attention of developers immediately.
Over time, error monitoring tools collect a wealth of data that can be analyzed to identify trends, joint issues, and areas of the application that are particularly error-prone. This insight can guide future development efforts and improve overall application stability.
In the past decade, JavaScript applications have become increasingly complex and powerful. These tools run on various devices, in varying network conditions and serve users worldwide.
As the demand for feature-rich and responsive web applications grows, developers face new challenges in ensuring their apps' reliability and performance. Therefore, JavaScript error monitoring and logging are essential for ensuring top-notch user experiences.
It's nearly impossible to catch every issue during development. JavaScript error logging helps identify and address problems before users experience or report them.
By implementing a robust error monitoring and logging strategy, developers can capture real-time data on errors:
By systematically tracking and analyzing errors, development teams can:
Implementing effective error monitoring strategies helps identify and resolve issues promptly and supports informed decision-making for continuous improvement.
Configuring allowed domains in your error monitoring tool ensures you only capture errors from trusted sources. In a typical web application, your code might interact with various domains, some of which could be loading:
These external sources can generate errors irrelevant to your application's core functionality. By setting up a whitelist of allowed domains, you can automatically filter out any errors that originate from domains not directly associated with your application.
If your app loads third-party scripts from another domain or if someone copies your JavaScript and runs it on a different site, errors from these sources won’t clutter your error logs. This way, you're notified only of issues that genuinely affect your app, making your monitoring process more focused and less noisy.
This practice is especially beneficial for large applications where unauthorized copying or extensive use of third-party scripts might be standard. By honing in on errors from your domain, you avoid chasing down issues that don't impact your users' experience with your application.
Browser extensions can introduce a lot of error noise by unexpectedly interfering with your JavaScript code. These extensions can modify the DOM, inject scripts, or override standard browser behaviors, leading to errors unrelated to your codebase.
To manage this, many error monitoring tools offer built-in mechanisms to ignore the mistakes caused by browser extensions automatically. If an error trace shows the origin of a file associated with a browser extension, it’s excluded from your logs. This feature saves you from spending time on errors that are out of your control and irrelevant to your application’s performance.
Filtering out errors from browser extensions is essential for keeping your error log clean. Without this, your monitoring dashboard could be flooded with non-actionable mistakes, making it harder to identify and prioritize real issues that affect your users.
Supporting older versions of browsers can be tricky because they often need more stability and provide limited debugging information. These outdated browsers might not support modern JavaScript features or offer detailed stack traces, making diagnosing and fixing errors challenging.
Given that the user base for older browsers is usually tiny and declining, it’s often more practical to ignore errors from these versions in your monitoring tool. By configuring your system to silence notifications from outdated browsers, you can focus on errors occurring in modern, widely-used browsers, where most of your users are likely to be.
This approach helps you allocate resources more effectively, ensuring your development efforts concentrate on improving the experience for most of your users. It also prevents your error logs from becoming cluttered with issues that are either unfixable or irrelevant due to the browser's outdated nature.
Source maps are invaluable when debugging minified JavaScript. When you deploy your application, the JavaScript code is often minified to improve performance. This process makes the code hard to read and debug, as the original variable names, function names, and formatting are lost.
A source map bridges the minified code and your source code, allowing your error monitoring tool to reverse-engineer the minified code into a more human-readable form. With source maps, when an error occurs, you can see the exact line of your original code where the error happened rather than trying to decipher a minified, often obfuscated version.
Source maps also enhance how errors are grouped by their root cause, ensuring that issues caused by the same underlying problem are clustered. This grouping helps you:
Without source maps, you’d have to trace errors to your original code manually:
Using source maps streamlines your debugging workflow, making identifying and resolving issues faster and easier.
Not all errors are equally critical. You might see thousands of error events in a large application, but their impact on users can vary widely. A critical error affecting many users is more urgent than a minor bug affecting only a few.
To manage your error resolution process effectively, it's essential to prioritize errors based on the number of users affected. Instead of focusing solely on the number of error events, look at the percentage of users encountering a particular error. This helps you prioritize bug fixes based on user impact.
Stability metrics, prioritized by user impact, can provide a broader view of your application's health. Metrics like session stability (the percentage of successful sessions over time) or user stability (the percentage of users who have experienced successful sessions) offer insights into your app's overall reliability. These metrics help you make data-driven decisions about where to focus your debugging efforts.
By prioritizing errors this way, you ensure that you address the issues affecting your users, leading to a more stable and reliable application.
Traffic Bot traffic, which includes both beneficial bots (like search engine crawlers) and harmful bots (such as those used for attacks or scraping), can generate many errors that don't reflect the actual user experience.
If your error monitoring tool doesn’t filter out bot traffic, your error logs could be noisy, making it difficult to identify genuine issues affecting human users. To tackle this, you can use custom filters to distinguish between bot traffic and fundamental user interactions.
Adding metadata to your error logs can tag errors as coming from bots or humans, allowing you to filter out bot-related errors from your main error-tracking dashboard. This ensures that your focus remains on issues impacting real users.
Creating bookmarks or custom views within your error monitoring tool that exclude bot traffic by default saves time. It also ensures your team is effectively debugging issues caused by non-human interactions.
Effectively managing bot traffic in your error monitoring helps maintain a more transparent, more accurate picture of your application’s health, leading to better decision-making and resource allocation.
Web applications are updated frequently, with new code being deployed regularly. Not all users will immediately refresh their browsers to load the latest version of your application. Some might keep a browser window open for days, running an older version of your code.
Assigning version numbers to each deployment to accurately track which version of your JavaScript code caused an error is essential. By tagging your JavaScript with a unique version number, you can quickly determine whether an error is occurring in the latest version of your code or in an older version that a user hasn’t refreshed.
Assigning version numbers allows you to see which errors are coming from old code versus new code. This information is critical for verifying whether a bug fix has been successful. If errors continue to be reported from the latest version, you know the issue still needs to be addressed.
Conversely, if mistakes only come from older versions, you can be confident that the current codebase has resolved the problem.
Versioning also helps in regression testing, allowing you to track when a previously fixed bug reappears in a new deployment. This practice ensures that you can maintain high confidence in your deployments and quickly identify and resolve any issues.
User Clickpaths Reproducing errors is one of the most challenging aspects of debugging, especially in JavaScript, where user interactions can be:
More than simply simply knowing that an error occurred is required; you need to understand the sequence of events that led up to the error to diagnose and fix it accurately.
Many error monitoring tools provide user session tracking, which allows you to capture the click path a user followed before encountering an error.
This includes every interaction the user had with your application—such as:
By analyzing the user’s journey, you can gain valuable insights into the conditions that triggered the error. This information makes it much easier to reproduce the issue in your development environment, enabling you to test potential fixes with greater confidence.
Reproducing errors based on user click paths helps you resolve issues more efficiently and improves your understanding of how users interact with your application. This can inform future development decisions, leading to a more robust and user-friendly product.
Error monitoring and logging techniques in JavaScript are used to track, identify, and handle errors within JavaScript code. When a program encounters an error, whether it’s a syntax mistake, a runtime issue, or a logical error, error monitoring tools help capture and record information about the error.
One way to capture errors in JavaScript is to use the built-in try/catch statement. This technique allows you to handle exceptions within a code block. The try block contains the code that might throw an error, and the catch block handles the error if one occurs.
Another way to monitor errors is to use the console outputs. This is a simple logging technique that outputs messages to the browser console. It’s commonly used for debugging purposes.
You can also create custom functions for error logging according to your web application's requirements.
The logging function can print the error details to the console, send them to a server, or customize the displayed information.
A JavaScript error monitoring tool is like your app's watchdog, monitoring everything that can go wrong while users use it.
When you're building a web application, there's always a chance that something might not work as expected—maybe a button doesn't do what it's supposed to, or a page doesn't load right. These issues are often caused by errors in the JavaScript code running behind the scenes.
So, what does a JavaScript error monitoring tool do? Think of it as an intelligent assistant that's always on duty. It watches over your app in real-time, detecting mistakes while users interact. When something goes wrong—like a function not working or a script crashing—it captures the details of the error, including:
But it doesn't stop there. These tools are designed to help you understand the context of the error, which is crucial for fixing it quickly. They'll give you insights into the browser the user was using, the specific line of code where the error occurred, and even what the user did right before it happened.
With all this information at your fingertips, you can prioritize and fix issues before they become more significant problems, ensuring your app runs smoothly for everyone. A JavaScript error monitoring tool is your early warning system, helping you catch and squash bugs before they affect too many users. It's a must-have to keep your app reliable and your users happy.
Alerty is a cloud monitoring service for developers and early-stage startups. It offers application performance monitoring, database monitoring, and incident management and supports technologies like:
Alerty helps developers identify and fix issues. The tool monitors databases such as:
It tracks key metrics, such as CPU and memory usage. To optimize user experience, it also features quick incident management and Real User Monitoring.
Alerty boasts a generous feature set for front end monitoring. Its Universal Service Monitoring covers dependencies like;
The tool uses AI to simplify setup, providing a cost-effective solution compared to competitors. It is designed for ease of use, allowing quick setup, and integrates with tools like Sentry, making it ideal for developers and small teams needing efficient, affordable monitoring.
Catch issues before they affect your users with Alerty's free APM solution today!
A tool that is by far one of the most used is Sentry. Sentry is an open-source error-tracking system with all the components necessary to start reporting errors out of the box. They use Raven.js, the official JavaScript client for Sentry, which can be incorporated into your application using their CDN.
The main benefit of Sentry is its ease of use. You can use classic try-catch styles when using the Raven client, and it allows you to easily hook this up to a data source name (DSN) they provide. The main disadvantage is you have to pay for such a great system. Working in a small team would cost you $29/month when this article was written.
Bugsnag is similar to Sentry, focusing on:
Bugsnag allows easy setup. A CDN link is provided to run Bugsnag on the client-side browser. You can install it through your favorite package manager, such as npm or yarn.
One of Bugsnag's neat features is breadcrumbs. Similar to informational logging, breadcrumbs can be written within your code to capture stateful information that may lead to a bug being thrown.
These breadcrumbs will then be logged along with the thrown error to give you increased contextual information. The one downside to Bugsnag is that you have to pay for it. At the time of writing, this platform also costs $29/month.
Raygun targets a market concerned with the visual aspects of error reporting. It is advertised as a workflow tool that can be set up to track down bugs and see if new releases resolve them.
With more messy integration steps into your JavaScript code than Sentry or Bugsnag, it allows you to integrate well into your client-side code and report on issues found. Raygun can give you a lot of configuration if you are not happy with the conventions it provides.
Ragun is very visual with its bug reports and progress tracking. Depending on your work, you may or may not find this beneficial. The biggest downside to Raygun is that it is a huge $199/month for even a startup to use.
The previous tools shown are tailored to many domains and programming languages. TrackJS specifically targets issues with client-side JavaScript error reporting.
This is an advantage, as it is a tool with a feature set tailored to JavaScript, so you won’t be paying for features you never use. Like the previous tools, it is easy to set up by adding script tags to your HTML.TrackJS gives you a dashboard that can show trends in errors, and even allow you to black box an error, reproducing the error locally to be able to fix costly issues.
The basic version of TrackJS is $29.99/month at the time of writing. This is slightly more expensive than Sentry and Bugsnag, which is interesting, considering TrackJS only works with JavaScript.
Usersnap takes JavaScript error monitoring in a different direction. It has a simplified way of recording client-side errors, with its main focus on user interaction and feedback. If you fancy a user-interactive solution, Usersnap can provide user feedback widgets and allow various integrations to provide timely feedback.
Usersnap allows you to integrate with many technologies, such as:
Like other tools, writing for one project and one team will cost you $29/month.
Alerty is a cloud monitoring service designed for developers and early-stage startups. It offers:
This tool supports popular technologies like:
If your app uses Next.js for fast static site generation, Alerty can help you monitor how your Next.js app performs in production while tracking any errors that occur. The tool also monitors databases like:
Alerty features quick incident management and Real User Monitoring (RUM) to optimize your user experience. Its Universal Service Monitoring covers dependencies like:
Alerty uses AI to simplify setup, providing a cost-effective solution compared to competitors. It is designed for ease of use, allowing quick setup, and integrates with tools like Sentry, making it ideal for developers and small teams needing efficient, affordable monitoring.
Alerty offers many features to help developers and startups track their applications' performance. Some of the key capabilities include:
Alerty’s APM helps you monitor your web applications built on JavaScript frameworks like Node.js, React, and Vue. You can track your app's production performance, including key metrics like:
The tool also helps you monitor the performance of specific services and APIs your app uses to identify external issues that may impact your user experience.
Alerty’s RUM capabilities allow you to track your web app’s performance from the perspective of your users. It collects data on how real users experience your application and helps you identify issues affecting user experience.
The tool also helps you monitor databases like:
You can track key performance metrics like:
Alerty features quick incident management so you can resolve issues affecting your application’s performance as quickly as possible. The tool helps you catch problems early before they impact your users.
Alerty’s Universal Service Monitoring tracks the performance of external services and APIs that your application uses. This includes monitoring dependencies like Stripe API and OpenAI to ensure they are functioning correctly and not causing issues for your users.
Alerty uses artificial intelligence to help:
Alerty integrates with various tools, including Sentry, to help you:
Alerty recently rebranded from its name, Metrilo, and is now explicitly focused on helping developers monitor their application's performance. The tool has added several new features, including iniversal service monitoring and AI-powered capabilities.