Why is there Unchecked lastError value when creating extensions for Firefox?

Rewrote the first test extension for Firefox from the documentation (https://developer.mozilla.org/en-US/docs/Mozilla/A... )

The extension simply adds to the page frame:
document.body.style.border = "5px solid yellow";

Open in the tab google.com and the console, there immediately error
Unchecked lastError value: Error: ID already exists: convert
Unchecked lastError value: Error: ID already exists: append

Why do they arise ?
5d48435719a66102387630.png
March 25th 20 at 13:28
0 answer

Find more questions by tags Mozilla FirefoxJavaScript