Youtube Video Quality

Disabling auto video quality with toast notification, original script -> https://greasyfork.org/en/users/226529

// ==UserScript==
// @name        Youtube Video Quality
// @version     1.05
// @grant       none
// @match       https://www.youtube.com/*
// @run-at      document-start
// @author      Yamako - Tanuki
// @description Disabling auto video quality with toast notification, original script -> https://greasyfork.org/en/users/226529
// @no-frames
// @namespace 
// ==/UserScript==

const QUALITIES =  ['auto', 'highres', 'hd2880', 'hd2160', 'hd1440', 'hd1080', 'hd720', 'large', 'medium', 'small', 'tiny'];
const QUALITY_MEDIUM = QUALITIES[8]; //360p
const QUALITY_LARGE = QUALITIES[7]; //480p
const QUALITY_SMALL = QUALITIES[9]; //240p
const KUALITAS = QUALITY_MEDIUM;
var entut = 0;
var kntd = 0;

addCSS('https://cdn.jsdelivr.net/npm/toastify-js/src/toastify.min.css');
addScript('https://cdn.jsdelivr.net/npm/toastify-js');

function SetQuality() {
  if (window.location.href.indexOf('watch?v=')>1){
    if (document.getElementById("movie_player").getPlaybackQuality() != KUALITAS &&
        document.getElementById("movie_player").getAvailableQualityLevels().indexOf(KUALITAS) > -1)
    {
      Toastify({text: "Change "+document.getElementById("movie_player").getPlaybackQuality()+" to "+ KUALITAS + " Quality.",duration: 3000}).showToast();
      document.getElementById("movie_player").setPlaybackQualityRange(KUALITAS);
    }
      else
    {
      if (entut == 0){
        Toastify({text: "Video Quality Already "+ document.getElementById("movie_player").getPlaybackQuality(),duration: 3000}).showToast();
        entut = 1;
      }
    }
  }
}

setTimeout(SetQuality, 1000);
setInterval(SetQuality, 500);


// https://makitweb.com/dynamically-include-script-and-css-file-with-javascript/
// Include CSS file
function addCSS(filename){
 var head = document.getElementsByTagName('head')[0];

 var style = document.createElement('link');
 style.href = filename;
 style.type = 'text/css';
 style.rel = 'stylesheet';
 head.append(style);
 console.log(filename + " Loaded.")
}

// Include script file
function addScript(filename){
 var head = document.getElementsByTagName('head')[0];

 var script = document.createElement('script');
 script.src = filename;
 script.type = 'text/javascript';

 head.append(script);
 console.log(filename + " Loaded.")
}