JSFiddle - React, Tailwind, and code Playground

CSS

.mystyle{
  background:red;
  color:white;
  border:1px solid black;
  margin:10px 0;
}

JavaScript

let week = ['Monday','Tuesday','Wednesday', 'Thursday', 'Friday', 'Saterday', 'Sunday'];
week.map(function(e,i){
	var div = document.createElement("div");
  if((i+1) == 5  || (i+1) == 6)
  	div.classList.add("mystyle");
  div.innerHTML = (i+1)+ " день "+" : "+e;
	document.body.appendChild(div);
});