JSFiddle - React, Tailwind, and code Playground

HTML

<div id="d1">Hello World</div>

CSS

.s1{
 background-color:blue;   
}
.s2{
 color:white;   
}

JavaScript

function AddClassToElement(elem,value){
 var rspaces = /\s+/;
 var classNames = (value || "").split( rspaces );
 var className = " " + elem.className + " ",
 setClass = elem.className;
 for ( var c = 0, cl = classNames.length; c < cl; c++ ) {
  if ( className.indexOf( " " + classNames[c] + " " ) < 0 ) {
   setClass += " " + classNames[c];
  }
 }
 elem.className = setClass.replace(/^\s+|\s+$/g,'');//trim
}
var el = document.getElementById("d1");
setTimeout(function(){
AddClassToElement(el,"s1");
},333);
setTimeout(function(){
AddClassToElement(el,"s2");
},667);  

function RemoveClassFromElement(elem,value){
     var rspaces = /\s+/;
     var rclass = /[\n\t]/g
     var classNames = (value || "").split( rspaces );
     var className = (" " + elem.className + " ").replace(rclass, " ");
     for ( var c = 0, cl = classNames.length; c < cl; c++ ) {
      className = className.replace(" " + classNames[c] + " ", " ");
     }
     elem.className = className.replace(/^\s+|\s+$/g,'');//trim
    }

setTimeout(function(){
RemoveClassFromElement(el,"s2");
},1000);      
setTimeout(function(){
RemoveClassFromElement(el,"s1");
},1333);