Introduction

In order to create custom validations rule for form fields, you can add the validation attribute to each field in the form configuration. For example:

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message defines the message to be displayed in case this validation has been failed.

Validation Engine: JavaScript (js)

This validation engine is the default engine. It takes a JavaScript expression using the rule attribute and evaluates it. In case it evaluates to false, the message given by attribute message is shown.

The field value is provided as variable val and can be used inside the rule expression.

Some examples

The given field is a required one. Therefore, make sure the field has a value. See the !! operator in JavaScript:

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