Why Does My Userscript Get a \'ReferenceError: Function Not Defined\' on HTML Element Click, and How Can I Fix It?

ReferenceError: Function Not Defined on HTML Element Click

Issue

When attempting to create a userscript to add custom emotes to a website, the error "Uncaught ReferenceError: function is not defined" occurs when clicking buttons with an onclick attribute.

Solution

The issue arises from the use of onclick attributes in the userscript. Userscripts run in a sandboxed environment separate from the target page, so onclick events created within the userscript cannot access functions defined in the page.

To resolve this, it is essential to use addEventListener() instead of onclick attributes. This ensures that event listeners are correctly added and can access functions defined within the userscript.

Example

Here's a revised version of the code that resolves the issue:

// Replace onclick attribute with event listener
emoteTab[2].innerHTML += '<span>

Additional Considerations

Data Attribute Usage:

Instead of passing data within the event handler's onclick attribute, as was attempted earlier, it's recommended to use data attributes to store the data in the HTML element itself.

ID Duplication:

Avoid reusing the same id for multiple elements, as it's an invalid practice that can lead to unexpected behavior.

innerHTML Overwrites:

When modifying the innerHTML of an element, any existing event handlers are removed. Therefore, it's crucial to recreate event listeners after making HTML changes.

The above is the detailed content of Why Does My Userscript Get a \'ReferenceError: Function Not Defined\' on HTML Element Click, and How Can I Fix It?. For more information, please follow other related articles on the PHP Chinese website!