How does form validation work?

You have three options:

• You can set simple expressions for each control in the Custom Validation field in the Other tab.

  

  Read more on this here.

• Another option is to use JavaScript in Action Handlers. To do that, declare the following function:

  {
    validate: function (args /*{data, originalData, state, component, formName, index, controlRef, eventArgs, isChild}*/){
        var errors = {};
        //TODO: Insert your code for validation this form
        if(data.name == undefined || data.name == ''){
            errors.name = 'This field is required!';
        }
        if(errors.name){
            throw {
                level: 1,
                message: 'Check errors on the form!',
                formerrors: errors
            };
        }
        return {};
    }
  }

• The third option is to use the server validation using triggers