@test-runner/web/ui/node_modules/obso/dist/index.js

web-runner

(function (global, factory) {
  typeof exports === 'object' && typeof module !== 'undefined' ? module.exports = factory() :
  typeof define === 'function' && define.amd ? define(factory) :
  (global = typeof globalThis !== 'undefined' ? globalThis : global || self, global.Emitter = factory());
}(this, (function () { 'use strict';

  /**
   * @module obso
   */
  const _listeners = new WeakMap();

  /**
   * @alias module:obso
   */
  class Emitter {
    constructor () {
      _listeners.set(this, []);
    }

    /**
     * Emit an event.
     * @param {string} eventName - the event name to emit.
     * @param ...args {*} - args to pass to the event handler
     */
    emit (eventName, ...args) {
      const listeners = _listeners.get(this);
      if (listeners && listeners.length > 0) {
        const toRemove = [];

        /* invoke each relevant listener */
        for (const listener of listeners) {
          const handlerArgs = args.slice();
          if (listener.eventName === '__ALL__') {
            handlerArgs.unshift(eventName);
          }

          if (listener.eventName === '__ALL__' || listener.eventName === eventName) {
            listener.handler.call(this, ...handlerArgs);

            /* remove once handler */
            if (listener.once) toRemove.push(listener);
          }
        }

        toRemove.forEach(listener => {
          listeners.splice(listeners.indexOf(listener), 1);
        });
      }

      /* bubble event up */
      if (this.parent) this.parent._emitTarget(eventName, this, ...args);
    }

    _emitTarget (eventName, target, ...args) {
      const listeners = _listeners.get(this);
      if (listeners && listeners.length > 0) {
        const toRemove = [];

        /* invoke each relevant listener */
        for (const listener of listeners) {
          const handlerArgs = args.slice();
          if (listener.eventName === '__ALL__') {
            handlerArgs.unshift(eventName);
          }

          if (listener.eventName === '__ALL__' || listener.eventName === eventName) {
            listener.handler.call(target, ...handlerArgs);

            /* remove once handler */
            if (listener.once) toRemove.push(listener);
          }
        }

        toRemove.forEach(listener => {
          listeners.splice(listeners.indexOf(listener), 1);
        });
      }

      /* bubble event up */
      if (this.parent) this.parent._emitTarget(eventName, target || this, ...args);
    }

     /**
      * Register an event listener.
      * @param {string} [eventName] - The event name to watch. Omitting the name will catch all events.
      * @param {function} handler - The function to be called when `eventName` is emitted. Invocated with `this` set to `emitter`.
      * @param {object} [options]
      * @param {boolean} [options.once] - If `true`, the handler will be invoked once then removed.
      */
    on (eventName, handler, options) {
      const listeners = _listeners.get(this);
      options = options || {};
      if (arguments.length === 1 && typeof eventName === 'function') {
        handler = eventName;
        eventName = '__ALL__';
      }
      if (!handler) {
        throw new Error('handler function required')
      } else if (handler && typeof handler !== 'function') {
        throw new Error('handler arg must be a function')
      } else {
        listeners.push({ eventName, handler: handler, once: options.once });
      }
    }

    /**
     * Remove an event listener.
     * @param eventName {string} - the event name
     * @param handler {function} - the event handler
     */
    removeEventListener (eventName, handler) {
      const listeners = _listeners.get(this);
      if (!listeners || listeners.length === 0) return
      const index = listeners.findIndex(function (listener) {
        return listener.eventName === eventName && listener.handler === handler
      });
      if (index > -1) listeners.splice(index, 1);
    }

    /**
     * Once.
     * @param {string} eventName - the event name to watch
     * @param {function} handler - the event handler
     */
    once (eventName, handler) {
      /* TODO: the once option is browser-only */
      this.on(eventName, handler, { once: true });
    }
  }

  /**
   * Alias for `on`.
   */
  Emitter.prototype.addEventListener = Emitter.prototype.on;

  return Emitter;

})));