`ontoggle` event handler support

[aristov]

Hello!

This code adds a support of the ontoggle event handler in Safari, which lacks this feature:

{
    const { HTMLElement : { prototype } } = window;
    if(!('ontoggle' in prototype)) {
        Object.defineProperties(prototype, {
            ontoggle : {
                configurable : true,
                enumerable : true,
                set(handler) {
                    this.__handler_ontoggle__ = typeof handler === 'function'?
                        handler.bind(this) :
                        null;
                },
                get() {
                    return this.__handler_ontoggle__;
                }
            },
            __handler_ontoggle__ : { writable : true, value : null }
        });
        document.addEventListener('toggle', event => {
            const target = event.target;
            if(typeof target.ontoggle) target.ontoggle(event);
        }, true);
    }
}

Usage:

const details = document.createElement('details');
details.ontoggle(handler);

I don't know CoffeeScript, sorry. And thanks for this stuff!

[Flimm]

According to caniuse, the latest version of Safari 10.1 does not have this issue any more. I haven't tested it myself.