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

machine.js

const fetchUser = userId =>
  fetch(`url/to/user/${userId}`).then(response => response.json());

const userMachine = Machine({
  id: 'user',
  initial: 'idle',
  context: {
    userId: 42,
    user: undefined,
    error: undefined
  },
  states: {
    idle: {
      on: {
        FETCH: 'loading'
      }
    },
    loading: {
      invoke: {
        id: 'getUser',
        src: (context, event) => fetchUser(context.userId),
        onDone: {
          target: 'success',
          actions: assign({ user: (context, event) => event.data })
        },
        onError: {
          target: 'failure',
          actions: assign({ error: (context, event) => event.data })
        }
      }
    },
    success: {},
    failure: {
      on: {
        RETRY: 'loading'
      }
    }
  }
});