Javascript中自定义事件

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);