In this post, we will cover in detail an error message that you will occasionally come across while building Angular applications: “Expression has changed after it was checked” - ExpressionChangedAfterItHasBeenCheckedError.

We are going to give a complete explanation about this error. We will learn why it occurs, how to debug it consistently and how to fix it.

Most of all we are going to explain why this error is useful, and how it ties back to the Angular Development Mode.

Table Of Contents

In this post, we will cover the following topics:

• Understanding the “Expression has changed” error, why does it occur?
• The Angular Development mode
• Debugging Techniques for finding the template expression that is causing the error
• How to fix the “Expression has changed” error
• Conclusions

We will first start by quickly debugging the error (a video is available for this), and then we will explain the cause and apply the fix. So without further ado, let’s get started!

#angular #javascript