EventTarget interface in safari

问题:

I started to extend the EventTarget interface by adding some useful prototypes but then I tested it on Safari 8 and get :

[Error] ReferenceError: Can't find variable: EventTarget

I found on MDN that "window.EventTarget does not exist" for Safari.

This question looks really interesting but it's about IE8.

So, I want to know if a reference to the EventTarget interface is accessible on Safari, or a workaround to use code like EventTarget.prototype.hasEventListener and EventTarget.prototype.hasEventListener without getting any errors on Safari ?

Edit I found an interesting commit which says that it was implemented the 09/12/15 (from timestamp), but it sure doesn't work in Safari 9.1

回答1:

Workaround :

I simply used the Element interface as a fallback for Safari

var EventTarget = EventTarget || Element;
EventTarget.prototype.addEventListener = function(){/*Some magic here*/};

I also checked that Element inherits prototypes from the EventTarget interface and it does ! (document.body.addEventListener == EventTarget.prototype.addEventListener returned true)

回答2:

Safari just doesn't allow you to use the EventTarget interface in your own objects other than DOM elements. So I simply replicated the class to do it.

class EventDispatcher {

    constructor() {
        this._listeners = [];
    }

    hasEventListener(type, listener) {
        return this._listeners.some(item => item.type === type && item.listener === listener);
    }

    addEventListener(type, listener) {
        if (!this.hasEventListener(type, listener)) {
            this._listeners.push({type, listener, options: {once: false}});
        }
        // console.log(`${this}-listeners:`,this._listeners);
        return this
    }

    removeEventListener(type, listener) {
        let index = this._listeners.findIndex(item => item.type === type && item.listener === listener);
        if (index >= 0) this._listeners.splice(index, 1);
//        console.log(`${this}-listeners:`, this._listeners);
        return this;
    }

    removeEventListeners() {
        this._listeners = [];
        return this;
    }

    dispatchEvent(evt) {
        this._listeners
            .filter(item => item.type === evt.type)
            .forEach(item => {
                const {type, listener, options: {once}} = item;
                listener.call(this, evt);
                if (once === true) this.removeEventListener(type, listener)
            });
        // console.log(`${this}-listeners:`,this._listeners);
        return this
    }
}