Front-end form, creating a tag Similar to the question asked here:
How to add a tags-field to an entry form?

I am trying to create an entry form that can create tags. I'm using http://selectize.github.io/selectize.js/ for the select element.

I am currently able to submit the form with existing tags but when trying to create a new tag using

$.post('/tags/createTag', data, function(response) {
    if (response.success) {
        alert('Success')
    } else {
        alert('Unable to create that tag.');
    }
});


I get http://talkbox.es:8888/index.php/tags/createTag 404 (Not Found)

Let me know if you guys need any more information, I'll gladly get it for you! Thanks a ton in advance.
It looks like you are not targeting the action URL. When accessing a Craft controller, you'll need to use the actionTrigger in your URL:

Your current URL:

http://talkbox.es:8888/index.php/tags/createTag


Should be updated to:

http://talkbox.es:8888/index.php/actions/tags/createTag


The actionTrigger is configurable so if you plan to reuse your code on multiple sites, you won't want to hard code that value. In twig, you can output that value using the craft.config variable:

{{ craft.config.actionTrigger }}