JSFiddle - React, Tailwind, and code Playground

HTML

<input type="checkbox" id="1" class="someclass" checked></input>
<input type="checkbox" id="2" class="someclass"></input>
<input type="checkbox" id="3" class="someclass"></input>
<input type="checkbox" id="4" class="someclass" checked></input>

JavaScript

var sum = 0;
$(".someclass:checked").each(function(){
    sum += Number(this.id);
})
   
alert(sum);