@t8/event-patterns/dist/index.js

Lightweight event emitter with flexible event type matching

// src/matchPattern.ts
function toObject(x) {
  return x.reduce((p, v, k) => {
    p[String(k)] = v;
    return p;
  }, {});
}
function matchPattern(pattern, value) {
  if (Array.isArray(pattern)) {
    for (let p of pattern) {
      let matches = matchPattern(p, value);
      if (matches) return matches;
    }
    return null;
  }
  if (pattern instanceof RegExp) {
    let matches = String(value).match(pattern);
    if (matches)
      return {
        ...toObject(Array.from(matches).slice(1)),
        ...matches.groups
      };
  }
  if (pattern === "*" || pattern === value)
    return {};
  return null;
}

// src/EventEmitter.ts
function getId() {
  return Math.random().toString(36).slice(2);
}
var EventEmitter = class {
  _listeners;
  constructor() {
    this._listeners = [];
  }
  on(type, handler) {
    return this._addListener(type, handler);
  }
  once(type, handler) {
    return this._addListener(type, handler, true);
  }
  addListener(type, handler) {
    return this._addListener(type, handler);
  }
  _addListener(type, handler, once = false) {
    if (typeof handler !== "function")
      throw new Error("handler is not a function");
    let id = getId();
    this._listeners.push({ id, type, handler, once });
    return {
      remove: () => this._removeListener(id)
    };
  }
  _removeListener(id) {
    for (let i = this._listeners.length - 1; i >= 0; i--) {
      if (this._listeners[i].id === id)
        this._listeners.splice(i, 1);
    }
  }
  emit(type, data) {
    let event = { type, data };
    for (let listener of this._listeners) {
      if (this.matches(listener, event)) {
        if (listener.once)
          this._removeListener(listener.id);
        listener.handler(this.toHandlerPayload(listener, event));
      }
    }
  }
  matches(listener, event) {
    return matchPattern(listener.type, event.type) !== null;
  }
  toHandlerPayload(listener, event) {
    let params = matchPattern(listener.type, event.type);
    return { ...event, params };
  }
};
export {
  EventEmitter,
  matchPattern
};