Map.set 链式调用实现状态机映射方法

const map = new Map();
console.log(map.set('a', 1)); // undefined
console.log(map.set('b', 2)); // undefined

class StateMap extends Map {
  set(key, value) {
    super.set(key, value);
    return this;
  }
  // 示例：添加状态转移注册能力
  transition(from, to, action) {
    const key = `${from}→${to}`;
    return this.set(key, action);
  }
  // 示例：触发状态迁移
  exec(from, to, ...args) {
    const handler = this.get(`${from}→${to}`);
    return handler && handler(...args);
  }
}

const orderFlow = new StateMap()
  .set('status', 'pending')
  .transition('pending', 'paid', (order) => {
    if (order.amount  {
    if (!order.warehouseReady) throw new Error('库存未就绪');
    order.status = 'shipped';
    updateLogistics(order);
  })
  .transition('shipped', 'completed', (order) => {
    order.status = 'completed';
    issueInvoice(order);
  });

const instanceStates = new WeakMap();
function getStateMap(obj) {
  if (!instanceStates.has(obj)) {
    instanceStates.set(obj, new StateMap());
  }
  return instanceStates.get(obj);
}
// 使用
const orderA = { id: 'A' };
getStateMap(orderA)
  .transition('pending', 'paid', () => console.log('A paid'))
  .set('current', 'pending');