JSFiddle - React, Tailwind, and code Playground

HTML

<div>
    <span id="a">1</span>
    <span id="a">2</span>
    <span>3</span>
</div>

JavaScript

$(function() {
    var w = $("div");
    console.log($('[id="a"]').length);
    console.log($('body [id="a"]').length);
    console.log($('[id="a"]', w).length);
});

$(document.getElementById('a')).css({"color":"orange"});