JSFiddle - React, Tailwind, and code Playground
HTML
<input type="checkbox" id="demo" />JavaScript
var cb = document.getElementById('demo');
console.log(cb.getAttribute('checked')); //沒有 checked 屬性.
console.log(cb.checked); // false
// 使用 jQuery .attr() & .prop()
console.log($(cb).attr('checked')); // undefined
console.log($(cb).prop('checked')); // false