index.js

var tablinks = document.getElementsByClassName("tab-links");
var tabcontents = document.getElementsByClassName("tab-contents");

function opentab(tabname){
    for(tablink of tablinks){
        tablink.classList.remove("active-link");
    }
    for(tabcontent of tabcontents){
        tabcontent.classList.remove("active-tab");
    }
    event.currentTarget.classList.add("active-link");
    document.getElementById(tabname).classList.add("active-tab");
}
var sidemeu = document.getElementById("sidemenu");
    function openmenu(){
        sidemeu.style.right = "0";
    }
    function closemenu(){
        sidemeu.style.right = "-200px";
    }