chrome undo the action of "prevent this page from creating additional dialogs"

Solution 1:

Close the tab of the page you disabled alerts. Re-open the page in a new tab. The setting only lasts for the session, so alerts will be re-enabled once the new session begins in the new tab.

Solution 2:

No. But you should really use console.log() instead of alert() for debugging.

In Chrome it even has the advantage of being able to print out entire objects (not just toString()).

Solution 3:

So the correct answer is: YES, there is a better way.

Right click on the tab and select "Duplicate", then close the original tab if you wish.

Alerting is re-enabled in the duplicate.

The duplicate tab seems to recreate the running state of the original tab so you can just continue where you were.