7.2 Custom Emitter's removeListener method is wrong

[waynnbz]

The removeLIstener method in the custom Emitter won't filter out the target listener. removeListener(eventName, listener) { const listeners = this.listeners[eventName] || [] listeners.filter(element => element === listener) this.listeners[eventName] = listeners }

In fact, the second line in the method listeners.filter(element => element === listener) won't make real modification to the listerners variable, and the original listeners will be returned.

Suggested modification as follow: removeListener(eventName, listener) { const listeners = this.listeners[eventName] || [] this.listeners[eventName] = listeners.filter(element => element !== listener) }