ninja-forms-three-custom-field-validation-2.js

var myCustomFieldController = Marionette.Object.extend({
  
    initialize: function() {

        // On the Form Submission's field validaiton...
        var submitChannel = Backbone.Radio.channel( 'submit' );
        this.listenTo( submitChannel, 'validate:field', this.validate );

        // on the Field's model value change...
        var fieldsChannel = Backbone.Radio.channel( 'fields' );
        this.listenTo( fieldsChannel, 'change:modelValue', this.validate );
    },
    
    validate: function( model ) {
      // Custom Validation Here...
    }
  
});