HTML form check if dot is used as delimiter

I'm working on a HTML form with two input fields: Amount and OrderID. In the Amount, the dot MUST be used as a delimiter, since the Javascript code that will process the form cannot handle the comma as a delimiter.

Is there a way to validate the form before submitting? Like some sort of "check input" button that checks if the entered data meets the criteria, and when OK, the Submit button can be pressed?

I've seen a lot of validation methods using PHP but I prefer to not use PHP since I'm working in Wordpress and don't want conflicting code (in my experience the PHP plugins in WP are not great).

-Ilse