The "MutationEvent is not defined" error frequently occurs in scripts that use outdated JavaScript functionality to monitor changes in the DOM (Document Object Model) of web pages. This error appears because MutationEvent is deprecated and is no longer supported in major modern browsers, including Google Chrome and Microsoft Edge.
What is MutationEvent and Why Was it Deprecated?
MutationEvent was used to monitor changes in HTML elements, but its deprecation highlighted MutationObserver, a more efficient API for handling the same needs.
Causes and Solution to the Issue
Likely Causes of the Error
- Outdated scripts, often found in third-party libraries or plugins.
- Specific functionalities that require monitoring changes in the DOM but still use MutationEvent instead of MutationObserver.
Quick Solution for Google Chrome and Microsoft Edge Users
To temporarily fix this issue, browsers offer an experimental option that can be enabled:
- Open the Chrome or Edge browser.
- In the address bar, type
chrome://flags(for Chrome) oredge://flags(for Edge). - In the options search box, enter "Mutation" and set the corresponding option to "Enable."
- Restart the browser to apply the changes.
Permanent Solution for Developers
To help developers implement a modern solution, here's an example of how to use MutationObserver:
Practical Video Solution
By following these steps, you can avoid the MutationEvent is not defined error, ensuring that your scripts continue to function correctly in modern browsers.