JSFiddle - React, Tailwind, and code Playground

HTML

<input type="checkbox" value="a" id="aa" checked/>a
<input type="checkbox" value="a1" id="aaa" checked/>a1
<input type="checkbox" value="a2" id="aaaa" checked/>a2
<input type="checkbox" value="a3" id="aaaaa" />a3
<button>Click</button>

JavaScript

$('button').click(function () {
    var dataString = {};
    $(':checkbox:checked').each(function () {
        var key = $(this).val();
        var value = $(this).attr('id');
        dataString[key] = value;
    });
    console.log(dataString);
});