JSFiddle - React, Tailwind, and code Playground

HTML

<div data-value="a"></div>
<div data-value="b"></div>
<div data-value="c"></div>
<div data-value="d"></div>
<div data-value="a"></div>
<div data-value="d"></div>
<div data-value="e"></div>

JavaScript

$( document ).ready(function() {
    var dataValues = $('div[data-value]').map(function(){
        return $(this).data("value");
    }).get();
    console.log($.unique(dataValues));
});