JSFiddle - React, Tailwind, and code Playground

HTML

<div class="plus">+</div>

<div class="res" ></div>

<div class="minus">-</div>

CSS

div{
  display:inline-block;
}

JavaScript

function buybalance(){
	var res = document.querySelector('.res');
 res.innerHTML = '2000';
  res.addEventListener('click', buy);
}

function buy(){
	this.innerHTML -= 500;
}
buybalance();

function plu(){

var get= document.querySelector('.plus');
get.addEventListener('click',pluLis); 

};
function pluLis(){
	var res = document.querySelector('.res');
res.innerHTML +=500;
};

plu();