@raulpesilva/re-state/es/core/observer.js

easy way to create a shared state to the entire application

import _createForOfIteratorHelperLoose from "@babel/runtime/helpers/esm/createForOfIteratorHelperLoose";
export var Observer = /*#__PURE__*/function () {
  function Observer() {
    this._listeners = new Map();
  }

  var _proto = Observer.prototype;

  _proto.subscribe = function subscribe(key, listener) {
    var _this = this;

    if (this._listeners.has(key)) {
      var listeners = this._listeners.get(key);

      this._listeners.set(key, [].concat(listeners, [listener]));
    }

    if (!this._listeners.has(key)) {
      this._listeners.set(key, [listener]);
    }

    return function () {
      var listenersCopy = [].concat(_this._listeners.get(key));

      var index = _this._listeners.get(key).indexOf(listener);

      if (index < 0) return;
      listenersCopy[index] = listenersCopy[listenersCopy.length - 1];
      listenersCopy.length--;

      _this._listeners.set(key, listenersCopy);
    };
  };

  _proto.notify = function notify(key) {
    if (this._listeners.has(key)) {
      for (var _iterator = _createForOfIteratorHelperLoose(this._listeners.get(key)), _step; !(_step = _iterator()).done;) {
        var listener = _step.value;
        listener();
      }
    }
  };

  return Observer;
}();