html5 video rateX (by Tampermonkey )

html-video-rateX.js

// ==UserScript==
// @name         video rateX
// @namespace    http://tampermonkey.net/
// @version      0.1
// @description  vdeio rateX
// @author       You
// @match        https://*/*
// @match        http://*/*
// @match        https://*.youtube.com/watch?v=*
// @match        https://*.instagram.com/*
// @match        https://*.facebook.com/*
// @grant        none
// ==/UserScript==
/*
Press Alt+5 to increase playbackRate and Alt+4 to decrease
*/
(function() {
    'use strict';

    setTimeout(()=>{
    document.addEventListener('keydown', (e)=>{
        if( e.altKey & (e.key == '5' || e.key == '4') ){
            document.querySelectorAll('video').forEach( o=>{
                o.playbackRate=o.playbackRate +(e.key == '5' ?0.5: -0.5);
                console.log('Up speed:'+o);
                document.body.insertAdjacentHTML('beforeend','<h1 id="_newRate" style="position:absolute; top:100px;left:200px; background-color:green;color:white;padding:1em;">x ' + o.playbackRate + '</h1>');
                setTimeout( ()=>{ document.getElementById('_newRate').remove() }, 3000 );

            } );
        }
    });
    }, 2000);

})();