pick up an appropriate validator from a list and check if transition is allowed

Script
const machine = Machine({
  id: 'machine',
  initial: 'A',
  states: {
    A: {
      on: {
        EVENT: [
          {
            target: 'B',
            actions: [
              'selectValidator',
              'validate'
            ]
          },
        ]
      }
    },
    B: {
      on: {
        EVENT: 'A'
      }
    }
  }
});

const guards = {
  selectValidator: context => {
    if (context.transition.event.type === 'EVENT') {
      context.validator = _someValidator
    }
  },
  validate: context => {
    if (context.transition.event.type === 'EVENT') {
      context.validator.validate(context)
    }
  }
}