JSFiddle - React, Tailwind, and code Playground

HTML

<div class="parent">
    <input type="checkbox" name="name1" />
    <input type="checkbox" name="name2" />
    <input type="checkbox" name="name3" checked="checked" />
    <input type="checkbox" name="name4" checked="checked" />
    <input type="checkbox" name="name5" />
</div>

JavaScript

var elements = document.querySelectorAll('.parent input:checked');
var names = Array.prototype.map.call(elements, function(el, i){
    return el.name;
});

console.log(names);