You can define your own Javascript custom validation calculation that will fire the same as the regular validators.
By selecting the validator type to calc and adding a calculation and error message you can have excellent control over validation.
// example JSON for an element with custom validation[ {"inputType":"text","label":"Some Password","model":"password1","placeholder":"","styleClasses":"col-md-3","type":"input","required":true,"validator":"string" }, {"inputType":"text","label":"Another Password","model":"password2","placeholder":"","styleClasses":"col-md-3","type":"input","required":true,"validator":"calc","validator_calc":"model.password1 == model.password2","errorMsg":"The passwords do not match" }]