Understanding the registration form

[md_]

Hi!

I would like to add some extra logic in my registration form and I'm super confused in terms of the button behavior. This is what currently exists there:

<div class="form-field action-bottom">
<input class="btn" onclick="Validate()" type="submit" value="{{ 'customer.register.submit' | t }}" />
</div>

The problem I have is that it seems there is no way to change the way this button acts. Removing the onlick="Validate()" function doesn't change anything in terms of the action that happens when the button is clicked. What's worse, is that I can create a button with absolutely nothing attached to it, like this:

<button type="test">Submit</button>

and it does the same action as the button above - it makes no sense at all.

Does anyone know what is the reason for this, and potentially how to change that? The purpose for me would be to add javascript validation for the fields I've created. At this point even if I overwrite the onclick="Validate()", it doesn't matter. 

Thanks in advance!