A simple pub/sub model - `set data()` - whenever this.data is changed the `set data()` gets called

Simple data watcher.js

function Store(initialData, options = {}) {
  const handlers = [];
  let nextHandlerId = 0;

  return {
    get data() {
      return initialData;
    },
    set data(t) {
      console.log("Set was called");
      handlers.forEach(handler => {
        handler.handler(t);
      });
    },
    set hoo(t) {
      console.log("Set hoo was called");
      handlers.forEach(handler => {
        handler.handler(t);
      });
    },
    watch(cb) {
      let ID = nextHandlerId++;
      handlers.push({
        id: ID,
        handler: cb
      });
      return ID;
    },
    unwatch(id) {
      for (let i = 0; i < handlers.length; i++) {
        if (handlers[i].id === id) {
          handlers.splice(i, 1);
          break;
        }
      }
    }
  };
}


  const TestStore = (function() {
    const store = Store(0);
    store.increment = function() {
      this.data = this.data + 1;
    };
    store.bla = function() {
      this.hoo = "bo";
    };
    return store;
  })();

  TestStore.watch(counter => {
    console.log("------>", counter);
  });
  TestStore.bla();
  TestStore.increment();