JSFiddle - React, Tailwind, and code Playground
HTML
<div a_example = "x" b_example = "y" class = "z"></div>
JavaScript
var elem = document.getElementsByClassName("z")[0],
a = elem.getAttribute("a_example");
console.log(a);
<div a_example = "x" b_example = "y" class = "z"></div>
var elem = document.getElementsByClassName("z")[0],
a = elem.getAttribute("a_example");
console.log(a);