Some bots usually get the textarea content by using document.getElementById("textAreaID").value
What I do is generate a random ID for every page refresh, ie:
<textarea id="random83721045">
</textarea>
Is there a way a javascript bot can bypass this random ID? And if so, is there a way to block this without using captcha?
A bot can get your textareas in any number of ways. If they want to use jquery, they can very easily target form elements by name.
Anti-spam measures are only effective on the server side.