Created
November 6, 2021 07:36
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An event emitter, with an event map
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// Usage: | |
// interface FooEventMap { | |
// run: (arg1: string, arg2: number) => void; | |
// } | |
// | |
// class Foo extends Emitter<{ [K in keyof FooEventMap]: FooEventMap[K] }> { | |
// run() { | |
// this.emit("run", "First argument", 5); | |
// } | |
// } | |
class Emitter<M extends { | |
[K in string]: (...args: any[]) => void | |
} = { [K in string]: (...args: any[]) => void }> { | |
protected _events: { [K in keyof M]?: M[K][] } = {} | |
on<K extends keyof M>(event: K, listener: M[K]) { | |
this._events[event] = this._events[event] || []; | |
this._events[event].push(listener); | |
} | |
once<K extends keyof M>(event: K, listener: M[K]) { | |
this._events[event] = this._events[event] || []; | |
const newListener = (...args: any[]) => { | |
// @ts-ignore | |
this.off(event, newListener); | |
listener.apply(this, args); | |
} | |
// @ts-ignore | |
this.on(event, newListener); | |
} | |
off<K extends keyof M>(event: K, listener: M[K]) { | |
this._events[event] = this._events[event] || []; | |
const listeners = this._events[event]; | |
const index = listeners.indexOf(listener); | |
if (index !== -1) listeners.splice(index, 1); | |
} | |
emit<K extends keyof M>(event: K, ...args: Parameters<M[K]>) { | |
this._events[event] = this._events[event] || []; | |
this._events[event].forEach((listener) => { | |
listener.apply(this, args); | |
}); | |
} | |
} | |
export default Emitter; |
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