Generated by XState Viz: https://xstate.js.org/viz

machine.js

const secretMachine = Machine({
  id: 'secret',
  initial: 'wait',
  context: {
    secret: '42'
  },
  states: {
    wait: {
      after: {
        1000: 'reveal'
      }
    },
    reveal: {
      type: 'final',
      data: {
        secret: (context, event) => context.secret
      }
    }
  }
});

const parentMachine = Machine({
  id: 'parent',
  initial: 'pending',
  context: {
    revealedSecret: undefined
  },
  states: {
    pending: {
      invoke: {
        id: 'secret',
        src: secretMachine,
        onDone: {
          target: 'success',
          actions: assign({
            revealedSecret: (context, event) => {
              // event is:
              // { type: 'done.invoke.secret', data: { secret: '42' } }
              return event.data.secret;
            }
          })
        }
      }
    },
    success: {
      type: 'final'
    }
  }
});