What Is Javascript Error Monitoring? 8 Best Practices For Monitoring Errors

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.

Table of Contents

• What Is Javascript Error Monitoring?
• Why Is Error Monitoring Crucial In Javascript?
• How To Manage Errors In JavaScript? 8 Best Practices for JavaScript Error Monitoring
• How Do You Capture Errors In JavaScript? Logging Errors In Javascript
• What Is The JavaScript Error Monitoring Tool?
• 6 Tools That Can Help You Manage Your JavaScript Error Reporting
• Catch Issues Before They Affect Your Users with Alerty's Free APM Solution

What Is Javascript Error Monitoring?

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.

JavaScript Error Tracking

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:

• Disrupt the user experience
• Cause features to malfunction
• Lead to security vulnerabilities

What JavaScript Error Monitoring Entails:

Real-Time Error Detection

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.

Error Logging

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.

Source Maps Integration

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.

User Session Tracking

Some monitoring tools offer user session tracking, allowing developers to see the events that led to an error. 

This can include:

• Every click
• Page load
• User interaction with the application before the error occurred making it easier to reproduce and fix the issue

Filtering and Noise Reduction

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.

Error Prioritization

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.

Alerts and Notifications

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.

Reporting and Analytics

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.

Related Reading

• Application Monitoring Best Practices
• Monitor Web Application
• Browser Monitoring
• End User Performance Monitoring
• Frontend Monitoring
• Front End Optimization
• E-Commerce Monitoring

Why Is Error Monitoring Crucial In Javascript?

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.

Why Errors Occur in JavaScript

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:

• Providing valuable insights for debugging
• Improving application performance

The Cost of Ignoring JavaScript Errors

By systematically tracking and analyzing errors, development teams can:

• Ensure a smoother user experience
• Reduce downtime
• Improve overall application performance

Implementing effective error monitoring strategies helps identify and resolve issues promptly and supports informed decision-making for continuous improvement.

How To Manage Errors In JavaScript? 8 Best Practices for JavaScript Error Monitoring

1. Configure Allowed Domains 

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:

• Debugging scripts
• Third-party libraries
• Even malicious code

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.

Domain-Specific Monitoring

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.

2. Strip Out Exceptions from Browser Extensions

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.

3. Ignore Old Browsers

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.

Prioritized Monitoring

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.

4. Use Source Maps

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.

Error Grouping

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:

• Identify patterns
• Prioritize fixes more effectively

Without source maps, you’d have to trace errors to your original code manually:

• A time-consuming
• Error-prone process

Using source maps streamlines your debugging workflow, making identifying and resolving issues faster and easier.

5. Prioritize Errors by Users Affected

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

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.

6. Filter for Bot 

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.

Filtering Out Bot Traffic

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.

Bookmarking Views

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.

7. Assign Version Numbers to Your JavaScript

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.

Version Tracking

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.

Regression Testing

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.

8. Reproduce Errors Using 

User Clickpaths Reproducing errors is one of the most challenging aspects of debugging, especially in JavaScript, where user interactions can be:

• Complex
• Unpredictable

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.

User Journey

This includes every interaction the user had with your application—such as:

• Clicks
• Form submissions
• Page navigation—leading up to the error

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.

Improved Understanding

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.

How Do You Capture Errors In JavaScript? Logging Errors In Javascript

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.

Outputting Error Details to the Console

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.

Creating Custom Error Logging Functions

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.

What Is The JavaScript Error Monitoring Tool?

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.

Intelligent Assistant

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:

• What caused it
• Where it happened
• How many users were affected

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. 

Early Warning

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.

Related Reading

• Front End Performance Testing
• End User Application Monitoring
• Frontend Performance
• Opentelemetry Browser
• Measure Page Load Time
• Javascript Performance Monitoring
• Front End Observability
• Front End Metrics
• Opentelemetry Frontend
• Datadog Pricing
• Sentry Pricing

6 Tools That Can Help You Manage Your JavaScript Error Reporting

1. Alerty: A Simple Yet Effective Solution for JavaScript Error Monitoring

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:

• NextJS
• React
• Vue
• Node.js.

Database Monitoring

Alerty helps developers identify and fix issues. The tool monitors databases such as:

• Supabase
• PostgreSQL
• RDS

It tracks key metrics, such as CPU and memory usage. To optimize user experience, it also features quick incident management and Real User Monitoring. 

Key Features

Alerty boasts a generous feature set for front end monitoring. Its Universal Service Monitoring covers dependencies like;

• Stripe API
• OpenAI
• Vercel

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!

2. Sentry: A Powerful Open-Source Option for JavaScript Error Tracking

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.

3. Bugsnag: Monitoring JavaScript Errors with Contextual Data

Bugsnag is similar to Sentry, focusing on:

• Error monitoring
• Web
• Mobile
• Server applications

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.

Breadcrumbs Feature

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.

4. Raygun: Targeting Visual Error Monitoring and Reporting

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.

Visual Reports

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.

5. TrackJS: A Tool Specifically for JavaScript Error Monitoring

The previous tools shown are tailored to many domains and programming languages. TrackJS specifically targets issues with client-side JavaScript error reporting.

Feature-Rich Tool

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.

6. Usersnap: JavaScript Error Monitoring with User Feedback

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:

• JIRA
• Asana
• Slack

Like other tools, writing for one project and one team will cost you $29/month.

Related Reading

• Dynatrace Pricing
• End User Experience Monitoring Tools
• Web Applications Monitoring Tools
• Logrocket Alternatives
• API Monitoring
• Bugsnag Alternatives
• Javascript Monitoring Tools
• Opentelemetry Alternatives
• End User Monitoring
• Pingdom Alternatives
• Manageengine Alternatives
• Rollbar Alternatives

Catch Issues Before They Affect Your Users with Alerty's Free APM Solution

Alerty is a cloud monitoring service designed for developers and early-stage startups. It offers:

• Application performance monitoring
• Database monitoring
• Incident management

This tool supports popular technologies like:

• NextJS
• React
• Vue
• Node.js, helping developers quickly identify and fix issues

Next.js Monitoring

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:

• SSupabase
• PostgreSQL
• RDS, tracking key metrics like CPU usage and memory consumption. 

Alerty features quick incident management and Real User Monitoring (RUM) to optimize your user experience. Its Universal Service Monitoring covers dependencies like:

• Stripe API
• OpenAI
• Vercel

AI-Powered Setup

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.

What Are The Key Features Of Alerty?  

Alerty offers many features to help developers and startups track their applications' performance. Some of the key capabilities include: 

Application performance monitoring (APM)  

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:

• Load times
• Errors 

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.

Real User Monitoring (RUM)

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.

Database Monitoring

The tool also helps you monitor databases like:

• PostgreSQL 
• Supabase

You can track key performance metrics like:

• CPU usage
• Memory consumption
• Query performance to identify issues before they impact your application’s performance

Incident Management

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.

Universal Service Monitoring

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.

Ai-Powered Features

Alerty uses artificial intelligence to help:

• Simplify the setup process
• Improve monitoring accuracy

Integrations

Alerty integrates with various tools, including Sentry, to help you:

• Streamline your workflow 
• Improve your application monitoring capabilities

What’s New In Alerty?

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.