State Machine

State machine components

import { entry, on, start } from "yieldmachine";

// This machine will load the passed URL.
function FetchMachine(url) {
  function fetchData() {
    return fetch(url);
  }
  
  function* idle() {
    yield on("FETCH", loading);
  }
  function* loading() {
    yield entry(fetchData);
    yield on("SUCCESS", success);
    yield on("FAILURE", failure);
  }
  function* success() {}
  function* failure() {
    yield on("RETRY", loading);
  }

  return idle;
}

// This machine will load our API.
function ExampleAPILoader() {
  const exampleURL = new URL("https://api.example.org/…");
  return FetchMachine(exampleURL);
}

// Start our API loader machine.
const loader = start(ExampleAPILoader);
loader.current; // "idle"

// Send the FETCH message to start loading.
loader.next("FETCH");
loader.current; // "loading"

loader.results.then((results) => {
  // Use response of fetch()
  console.log("Fetched", results.fetchData);
  loader.current; // "success"
});