Enables to control your Subsonic with Media Key.

media-key-for-subsonic-5.user.js

// ==UserScript==
// @name         Media Key for Subsonic 5
// @namespace    http://utgw.net/
// @version      0.1
// @description  Enables to control your Subsonic with Media Key.
// @author       utgwkk
// @match        https?://*/subsonic/index.view
// @require      https://cdnjs.cloudflare.com/ajax/libs/babel-core/5.6.15/browser-polyfill.min.js
// @require      https://cdnjs.cloudflare.com/ajax/libs/babel-core/5.6.15/browser.min.js
// ==/UserScript==

/* jshint ignore:start */
var inline_src = (<><![CDATA[
/* jshint ignore:end */
/* jshint esnext: true */
    (()=>{
        window.addEventListener('load', ()=>{
            const pf = document.getElementsByClassName('bgcolor2')[2];
            const cw = pf.contentWindow;
            const jw = cw.jwplayer;
            window.addEventListener('keydown', (evt)=>{
                if(evt.keyCode == 179){ // play/pause
                    const state = jw().getState();
                    if(state == "PLAYING"){
                        jw().pause();
                    }else if(state == "PAUSED"){
                        jw().play();
                    }
                }else if(evt.keyCode == 39 || evt.keyCode == 176){
                    cw.onNext();
                }else if(evt.keyCode == 37 || evt.keyCode == 177){
                    cw.onPrevious();
                }
            });
        });
    })();
/* jshint ignore:start */
]]></>).toString();
var c = babel.transform(inline_src);
eval(c.code);
/* jshint ignore:end */

How do we use/implement this?