Is creating an extension the only solution for validating custom fields?

Technical Q&A
1

In my frontend store I have a custom line property like so:

In case the user inputs a value greater than 99 or less than 1, I want to assign the object property.last in ‘{% for property in item.properties’ %}'s body to 99 and 1 respectively. But since property.last is an immutable object is creating a new extension just to validate two of my custom fields the only way to go?

2

Why you are not using JavaScript without creating a new extension? Add a script that listens for form submission, checks the value of your custom property input, and updates the value if it’s outside the desired range before the form is submitted.

3

Yes I’ve done that. What I’m looking for is a server side validation.