how can I disable the syntax checker in ACE editor?

There's a more efficient way of achieving this. Instead of spawning a worker for stopping it immediately after, is better to directly tell the editor to not spawn a worker, like this:

ace.edit(document.getElementById('test'), {
    useWorker: false
});

I also didn't find this in documentation, so I've looked at ACE source code. You can disable worker with the following lines of code:

var editor = ace.edit(document.getElementById('test'));
editor.getSession().setUseWorker(false);