Codigo em JS para Ajax

Pessoal, eu tenho um arquivo que ele ta em JavaScript. Nele seleciona através do getElement. Mais na mesma pagina preciso usar várias vezes esses 'itens' que esta selecionando. Teria como algum expert em ajax podesse rescrever para ajax ? Assim seria melhor para eu selecionar com class.

var vid, playbtn, seekslider, curtimetext, durtimetext, mutebtn, volumeslider, fullscreenbtn;
function intializePlayer(){

// Set object references

vid = document.getElementById("my_video");
playbtn = document.getElementById("playpausebtn");
seekslider = document.getElementById("seekslider");
curtimetext = document.getElementById("curtimetext");
durtimetext = document.getElementById("durtimetext");
mutebtn = document.getElementById("mutebtn");
volumeslider = document.getElementById("volumeslider");
fullscreenbtn = document.getElementById("fullscreenbtn");

// Add event listeners

playbtn.addEventListener("click",playPause,false);
seekslider.addEventListener("change",vidSeek,false);
vid.addEventListener("timeupdate",seektimeupdate,false);
mutebtn.addEventListener("click",vidmute,false);
volumeslider.addEventListener("change",setvolume,false);
fullscreenbtn.addEventListener("click",toggleFullScreen,false);
}
window.onload = intializePlayer;
function playPause(){
if(vid.paused){
vid.play();
playbtn.innerHTML = "<i class='fa fa-pause' aria-hidden='true'></i>";

} else {

vid.pause();
playbtn.innerHTML = "<i class='fa fa-play' aria-hidden='true'></i>";
}
}
function vidSeek(){
var seekto = vid.duration * (seekslider.value / 100);
vid.currentTime = seekto;
}
function seektimeupdate(){
var nt = vid.currentTime * (100 / vid.duration);
seekslider.value = nt;
var curmins = Math.floor(vid.currentTime / 60);
var cursecs = Math.floor(vid.currentTime - curmins * 60);
var durmins = Math.floor(vid.duration / 60);
var dursecs = Math.floor(vid.duration - durmins * 60);

if(cursecs < 10){ cursecs = "0"+cursecs; } if(dursecs < 10){ dursecs = "0"+dursecs; } if(curmins < 10){ curmins = "0"+curmins; } if(durmins < 10){ durmins = "0"+durmins; }

curtimetext.innerHTML = curmins+":"+cursecs;
durtimetext.innerHTML = durmins+":"+dursecs;
}
function vidmute(){
if(vid.muted){
vid.muted = false;
mutebtn.innerHTML = "<i class='fa fa-volume-up' aria-hidden='true'></i>";
document.getElementById("volumeslider").style.opacity='1';

} else {

vid.muted = true;
mutebtn.innerHTML = "<i class='fa fa-volume-off' aria-hidden='true'></i>";
document.getElementById("volumeslider").style.opacity='0';
}
}
function setvolume(){
vid.volume = volumeslider.value / 100;
}
function toggleFullScreen(){
if(vid.requestFullScreen){
vid.requestFullScreen();
} else if(vid.webkitRequestFullScreen){
vid.webkitRequestFullScreen();
} else if(vid.mozRequestFullScreen){
vid.mozRequestFullScreen();
}
}