Answer 1

Do you mean "easy" to win, or "slowly" played at computer turn?

In first case, simply replace AI by a basic random choice of cell to play...

In second case, better way is to use window.setTimeout() method to delay the script before computer turn play (this could require some attention to used variable scopes, as this introduce asynchronious execution -- so context is loosed -- but it's better practice than doing infinite loop exiting when delay is reached -- this will block the whole page execution/refresh until the delay was reached, using 100% of cpu, even if only one core, and disabled any user interaction with the page)...