JavaScript Errors

JavaScript is awesome and it has many advantages that enhance your web-site. The client-side JavaScript comes with excellent and extensive capabilities for powering the functionalities of modern web-based applications. However, if you do not understand the quirks that make the script work, the performance of your applications can be crippled.
JavaScript Error handling

JavaScript Debugging

JavaScript is criticized as a language that is quite difficult to debug . While programs written in JavaScript are larger, debugging and managing these scripts are getting more difficult especially due to the dynamic features of JavaScript. But you can significantly reduce this quality cost by catching code defects at the earlier stage of the development cycle .


When executing JavaScript code , different errors can occur. Some JavaScript errors can be very difficult to understand at first, and the line numbers given aren't always helpful either. Most of the errors that occur when the web-browser compiles the JavaScript are either undefined or null type errors. If the developer uses the strict compiler in a static checking system like Typescript, most of these errors can be avoided. It will give the warning that a type is not defined but expected. Even if Typescript is not used, guard clauses can be used to check if the objects are undefined before they are used.

There are many types of errors but they typically fall into one of 3 classes.

  1. TypeError - These errors occur when some value is not the type it's expected to be.

  2. SyntaxError - These errors occur when the JavaScript engine is parsing a script and encounters syntactically invalid code.

  3. ReferenceError - These errors occur when code refers to a value that does not exist in the current scope.
Rollbar did an interesting experiment. They've collected all the errors they faced and summarized how many times each one occurred. That helped to see the actual statistics with the most spread JavaScript errors .

Type of errors in JavaScript
Different browsers can give you different messages for the same error, so there are several different examples where applicable. In the following articles, we will look at the errors commonly faced by developers in their client-side JavaScript application and how to minimize or get rid of them.