How To Log Javascript Errors – Troubleshooting JavaScript errors in a production environment can be a difficult experience. Often, error reports are vague, and root causes are difficult to pinpoint. There are some general steps for identifying and resolving bugs that crop up in production.
In software development, the first step in debugging any problem is to try to replicate the scenarios. In most programming languages, this is reinforced by reviewing the logs that lead to the error, but with client-side JavaScript, this type of diagnosis requires significant foresight (see below).
How To Log Javascript Errors
Before we can reproduce any problem scenario, and assuming we have access to any product logs, we need to establish some testing guidelines first. This includes mirroring the production database, associated user accounts, and the operating system. Everything is fair game here.
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Once you’ve determined the conditions you think might cause a hunt exception or error, it’s time to test them. Never check production exceptions. Development and staging environments are designed to be breakable without impacting end users
More information is always better. Where are JavaScript errors logged? Using the methods described in the first step in locating any problem is to increase the amount of data you record. This allows you to see everything that is happening
A problem occurs. There’s a good chance that the problems you’re dealing with have potential warnings associated with warnings that aren’t necessarily in the logs by default.
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If you can’t reproduce the problem in step 2, it’s back to the drawing board. Not every bug is easy to reproduce, and time-based or other limitations can make it difficult to reproduce in a non-production environment. Go back to step 1, adjust your test parameters and try again.
In a production environment, JavaScript files are often compressed. While this is a great way to speed up any application, it can make debugging a nightmare because the files you’re trying to debug are nearly unreadable. This is where source maps come into play. Supported by most modern browsers, a source map is a file that maps uncompressed code to compressed code, allowing you to see what’s happening in a production environment.
While most minification tools have built-in support for source graphics, it’s important to understand how the browser associates compressed code with uncompressed code. In short, it comes in the form of a comment in a zipped JavaScript file that points directly to the source map.
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For example, let’s look at the developer console without source maps enabled. In particular, do you see how the source file says “Generated by CopyScript” and the auto-generated JavaScript underneath?
While the production JavaScript file can be viewed and debugged, it is not the code I wrote. The original source file is written in CopyScript, which means that any insights gained from the compiled code must be translated back into the original source file.
If source mapping is enabled, a breakpoint in the compile script can be mapped directly to the original CoffeeScript source file. This allows debugging in the context of source files rather than fancy and refined files.
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Layer footprint? In fact, this is an overview of every file and function that can lead to an error. To be clear, the stack trace does not include files and functions that have been touched
An error occurred, and only a chain of methods called the error occurred. This allows you to “search” the “stack” of the actions performed when an error occurred, and find out exactly what went wrong and where.
For example, let’s look at the stack trace returned from the following (incredibly simple) code:
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As you can see, instead of simply returning the exception message, reading the stack trace in reverse order shows that the exception was thrown on line 1 in column 7, but was triggered by a call to do_the_thing() on line 2 in column 9. For more complex stack traces, this could be Very valuable as it provides a lot of postmortem information.
While finding errors through log files works in some cases, sometimes it requires a bit more effort. Fortunately, most browsers allow you to pause running scripts and use them to diagnose problems as they occur. While doing so, variables and properties can be viewed and edited, giving you complete control over the state of any script that runs to identify it.
Browser-based debugging is an incredibly powerful tool, but the basic idea behind using it is to add breakpoints at points in your codebase where you want to look deeper into the layer and scope of the script. When the debugger encounters these breakpoints, all processing is suspended and you are given the opportunity to review the values of any variables, change them to test better assumptions, and fix any problems encountered.
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While built-in debugging is great for many use cases, it’s important to note that introducing advanced JavaScript platforms like Vue.js and Redux can make using the debugger more complex. This is where browser-based plugins like Vue.js devtools and Redux DevTools come into play. These tools are designed with the complexity of their target platforms in mind, enabling more focused debugging of more complex code bases.
While in-browser debugging is great for client-side JavaScript, Node.js ships with its own debugger for server-side debugging. Debugging Node.js code can be done by inspecting Node.js in the source file or using any of the major IDE combinations designed for debugging Node.js.
The challenge when debugging in production is that you don’t have access to the user’s developer console. To gather enough context to diagnose a problem, you need to track information in a central location accessible to your developers. Traditionally, this is done using logs, but there is a better way.
Javascript Error Logging
. Instead of sorting through pages of raw text logs, it aggregates outliers and individual errors to create a dashboard with as much information as possible to analyze these issues.
When properly configured, these exceptions are directly tied to user accounts and are punched over time using easy-to-read layout markers on the start chart. It doesn’t necessarily tell you exactly
One problem is that it comes as close as possible to doing this by giving you more information than you can ask for.
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Telemetry, unique to the JavaScript integration, is advanced event tracking that lets you track what’s happening in the moments leading up to and immediately after an error. This is incredibly valuable because it gives you the ability to see any behavior that might lead to an error being thrown inadvertently.
Whenever an exception is thrown during an HTTP request, the request details are tracked along with additional information such as browser and operating system. This gives you the ability to identify potential problems related to specific settings, or monitor parameters of abusive requests.
If you follow the deployments in , it is as simple as possible to determine which deployment is responsible for the new error or exception. So simple, in fact, that it works for you.
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When a project is linked to a GitHub, Bitbucket, or GitLab repository, any file references in the Stack Trace are automatically linked directly to the offending file in the linked repository. We detect and fix bugs on your site automatically for you. A view of how the user encountered the error.
JavaScript errors are unpredictable. Debugging and checking user reports can be annoying, time-consuming and expensive. JavaScript makes error handling easy and accessible to your entire team. With our easy-to-use reports and clear alerts, you’ll see and understand errors in your home code with a fast debugging environment.
We do not charge for our service based on the number of errors or events you submit. This does not direct us to help you fix bugs! We want to be your partners and succeed when you succeed.
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