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JavaScript Error Handling: Inspect Chrome Error Log in DevTools

Reading time 4 min
Published Feb 14, 2018
Updated Oct 3, 2019

More than one command can be used to print messages to the Console panel of Chrome DevTools. Why is that? Well, some logging practices can be used to indicate the severity of the logged data. For instance, a Chrome error log that requires immediate fixing should stand out from the rest of the logs.

Diagnosed errors can be found in the Console panel, from which you should take the first steps towards JavaScript error handling. Other tabs of DevTools also play a role in the error-handling process, but more on that later.

The Console panel offers a set of features, designed for JavaScript error checking. With this Chrome tab, you can review all of the errors and inspect them.

Since the Console panel provides a lot of details about every Chrome error log, it is easy to implement in-depth analysis and find possible solutions. Therefore, if you notice issues on your website, exploit the functions in the Console panel to start JavaScript error handling.

In the Console panel, you can stop the execution of JavaScript at any moment. This feature is crucial for JavaScript error handling as you will be able to inspect the specific moment when the script goes wrong. Additionally, you are welcome to use the JavaScript error handler to collect data about runtime expressions.

Don’t let errors overshadow the purpose of your website: fix issues now!

JavaScript Error Handling: Main Tips

  • In this tutorial, we explain how you can deal with various errors and exceptions that are logged to the Console panel.
  • The Console allows you to track the errors and exceptions that pop up, so you can get details behind them and find the causes.

Error Handling Explained

JavaScript error handling combines the use of several panels of DevTools: Console and Sources.

Firstly, let's assume an error or exception has occurred on your page.

After noticing that there is something wrong, you may open the Console to inspect and find an error.

On the right side of the error log, you will notice its source (to which you can navigate). The source may be an URL or a line in one of the page's files.
Javascript Error Handling
It is also useful to know how the error's stack trace is viewed.

In the example below, stack frames, related to the error, are shown. You can easily navigate to them. As a result, you will understand the cause of the error better.

Javascript Error Handling

You also have the option to pause the execution of the code on exceptions.

Javascript Error Handling

These functions make the process of JavaScript error checking much smoother.

Usage of Stack Trace

Chrome Developer Tools allow you to inspect how websites work in more depth. Because you can review associated stack traces, the logs become more informative.

We will now look at the options for working with stack traces.

error.trace

Each error object has a string property named stack. This property contains the stack trace, which can tell you more about the source of the problem.

console.trace()

The console.trace() command makes the console print the current call stack. The command will let you see what's going on at key moments.

console.assert()

This command gives you more control, since using it allows you to set the conditions for errors. If the provided expression evaluates to false, an error message will be displayed.

Note: Read more about console.assert() and console.trace() in our tutorial on the Console API.

Command to Find Runtime Exceptions

Another important subject we should cover is handling runtime exceptions.

To begin with, we should explain how the window.onerror handler function can help you implement JavaScript error handling. The command is meant for detecting issues that were not present during testing.

When a JavaScript exception gets thrown but is not caught by catch/try code clock, this function is invoked along with:

  • A message related to the error.
  • An URL of the resource that the exception originates from.
  • The line of the resource in which the exception occurs.

These three are passed as three arguments (in the order shown above).

JavaScript Error Handling

It is also possible to set a JavaScript error handler, which collects all of this error-related information. It can then be sent to the server using an AJAX POST call. Therefore, this command allows you to collect information about the runtime exceptions that users experience on your website.

JavaScript Error Handling: Summary

  • This tutorial informed you of the ways the Console panel of Chrome DevTools can be used to manage errors and exceptions.
  • The panel lets you implement detailed analyses about the diagnosed errors and exceptions. From such detailed investigations, developers are likely to debug errors faster.