events.js

(function (global, factory) {
  if (typeof define === "function" && define.amd) {
    define(["exports"], factory);
  } else if (typeof exports !== "undefined") {
    factory(exports);
  } else {
    var mod = {
      exports: {}
    };
    factory(mod.exports);
    global.events = mod.exports;
  }
})(typeof globalThis !== "undefined" ? globalThis : typeof self !== "undefined" ? self : this, function (_exports) {
  "use strict";

  Object.defineProperty(_exports, "__esModule", {
    value: true
  });
  _exports["default"] = void 0;

  function _createForOfIteratorHelper(o, allowArrayLike) { var it = typeof Symbol !== "undefined" && o[Symbol.iterator] || o["@@iterator"]; if (!it) { if (Array.isArray(o) || (it = _unsupportedIterableToArray(o)) || allowArrayLike && o && typeof o.length === "number") { if (it) o = it; var i = 0; var F = function F() {}; return { s: F, n: function n() { if (i >= o.length) return { done: true }; return { done: false, value: o[i++] }; }, e: function e(_e) { throw _e; }, f: F }; } throw new TypeError("Invalid attempt to iterate non-iterable instance.\nIn order to be iterable, non-array objects must have a [Symbol.iterator]() method."); } var normalCompletion = true, didErr = false, err; return { s: function s() { it = it.call(o); }, n: function n() { var step = it.next(); normalCompletion = step.done; return step; }, e: function e(_e2) { didErr = true; err = _e2; }, f: function f() { try { if (!normalCompletion && it["return"] != null) it["return"](); } finally { if (didErr) throw err; } } }; }

  function _unsupportedIterableToArray(o, minLen) { if (!o) return; if (typeof o === "string") return _arrayLikeToArray(o, minLen); var n = Object.prototype.toString.call(o).slice(8, -1); if (n === "Object" && o.constructor) n = o.constructor.name; if (n === "Map" || n === "Set") return Array.from(o); if (n === "Arguments" || /^(?:Ui|I)nt(?:8|16|32)(?:Clamped)?Array$/.test(n)) return _arrayLikeToArray(o, minLen); }

  function _arrayLikeToArray(arr, len) { if (len == null || len > arr.length) len = arr.length; for (var i = 0, arr2 = new Array(len); i < len; i++) { arr2[i] = arr[i]; } return arr2; }

  function _classCallCheck(instance, Constructor) { if (!(instance instanceof Constructor)) { throw new TypeError("Cannot call a class as a function"); } }

  function _defineProperties(target, props) { for (var i = 0; i < props.length; i++) { var descriptor = props[i]; descriptor.enumerable = descriptor.enumerable || false; descriptor.configurable = true; if ("value" in descriptor) descriptor.writable = true; Object.defineProperty(target, descriptor.key, descriptor); } }

  function _createClass(Constructor, protoProps, staticProps) { if (protoProps) _defineProperties(Constructor.prototype, protoProps); if (staticProps) _defineProperties(Constructor, staticProps); return Constructor; }

  function checkListener(input) {
    if (typeof input !== 'function') throw new TypeError('Listener must be a function');
  }

  var EventEmitter = /*#__PURE__*/function () {
    function EventEmitter() {
      _classCallCheck(this, EventEmitter);

      this.bus = new Map();
    }

    _createClass(EventEmitter, [{
      key: "on",
      value: function on(event, listener) {
        checkListener(listener);
        var bus = this.bus;
        var listeners;

        if (bus.get(event)) {
          listeners = bus.get(event);
        } else {
          listeners = [];
          bus.set(event, listeners);
        }

        listeners.push(listener);
        var removeIndex = listeners.length - 1;
        var flag = true;
        return function remove() {
          if (flag) {
            // can only remove once
            listeners.splice(removeIndex, 1);
            flag = false;
          }
        };
      }
    }, {
      key: "emit",
      value: function emit(event) {
        var listeners = this.bus.get(event);
        if (!listeners) return;

        for (var _len = arguments.length, args = new Array(_len > 1 ? _len - 1 : 0), _key = 1; _key < _len; _key++) {
          args[_key - 1] = arguments[_key];
        }

        var _iterator = _createForOfIteratorHelper(listeners),
            _step;

        try {
          for (_iterator.s(); !(_step = _iterator.n()).done;) {
            var listener = _step.value;
            if (typeof listener === 'function') Reflect.apply(listener, this, args);
          }
        } catch (err) {
          _iterator.e(err);
        } finally {
          _iterator.f();
        }
      }
    }]);

    return EventEmitter;
  }();

  var _default = EventEmitter;
  _exports["default"] = _default;
  module.exports = exports.default;
});