GeminiにcreateSignal作らせた

createSignal1.js

function createSignal(value) {
  const subscribers = new Set();

  const read = () => {
    if (currentComponent) {
      subscribers.add(currentComponent);
    }
    return value;
  };

  const write = (newValue) => {
    if (value !== newValue) {
      value = newValue;
      subscribers.forEach((subscriber) => subscriber());
    }
  };

  return [read, write];
}

let currentComponent = null;

function effect(fn) {
  currentComponent = fn;
  fn();
  currentComponent = null;
}

document.body.innerHTML = `
  <div id="count"></div>
  <button id="up">Increment</button>
`;

const [count, setCount] = createSignal(0);

effect(() => {
  document.getElementById("count").textContent = `Count: ${count()}`;
});

document.getElementById("up").addEventListener("click",() => {
  setCount(count() + 1);
})

createSignal2.js

function createSignal<T>(initialValue: T): [() => T, (newValue: T) => void, (subscriber: () => void) => void] {
  let value = initialValue;
  const subscribers = new Set<() => void>();

  const read = () => {
    return value;
  };

  const write = (newValue: T) => {
    value = newValue;
    subscribers.forEach((subscriber) => subscriber());
  };

  const subscribe = (subscriber: () => void) => {
    subscribers.add(subscriber);
  };

  return [read, write, subscribe];
}

const [count, setCount, subscribeCount] = createSignal(0);

subscribeCount(() => {
  console.log("Count changed:", count());
});

setCount(1); // "Count changed: 1" と出力される