JSFiddle - React, Tailwind, and code Playground

HTML

Product 1: <button id="product1">Add one</button>
<br>
Product 2: <button id="product2">Add one</button>
    
<div></div>

JavaScript

var cart = [];

$(document).ready(function(){
    
     $('button').on('click', function() {
    
			cart.push( { id:$(this).attr('id'), qty:1 } );

			var result = cart.reduce(function(res, obj) {
                
                if (!(obj.id in res )) {
                    res[obj.id] = 0
                }     
                return ( res[obj.id] += obj.qty ) && res ;               
            }, {} )
       
            console.log( result )
	});
});