class CustomEvent { constructor() { // { // eventName: []; // } this.eventsKeeper = {}; } isAssigned(name, cb) { const keeper = this.eventsKeeper; if (!cb) { return name in keeper; } else { return name in keeper && keeper[name].indexOf(cb) !== -1; } } on(name, cb) { const keeper = this.eventsKeeper; const cbs = keeper[name]; if (this.isAssigned(name, cb)) return; if (!cbs) { keeper[name] = [cb]; } else { keeper[name].push(cb); } } emit(name, ...rest) { if (this.isAssigned(name)) { this.eventsKeeper[name].forEach(cb => { cb(...rest); }); } else { throw Error(`you may not listen [${name}] event!`); } } remove(name) { if (!name) return; delete this.eventsKeeper[name]; } } // test // node test.js // const event = new CustomEvent(); // event.on("test", (first, second) => { // console.log(`${first} ${second}`); // console.log("it is ok"); // }); // event.on("test", () => { // console.log("it is line ok"); // }); // event.remove("test"); // event.on("line", () => { // console.log("it is line ok "); // }); // event.emit("line"); // setTimeout(() => { // event.emit("test", "hello", "world"); // }, 2000);