JSFiddle - React, Tailwind, and code Playground

HTML

<span id="test-1">This text should be blue</span>
<span id="test-2" data-test="example">This text should be red</span>

CSS

body {
  color: #00F;
}

[data-test] {
  color: #F00;
}

JavaScript

(function () {
  var t1,
      t2;
  t1 = $('#test-1').attr('data-test');
  t2 = $('#test-2').attr('data-test');

  $('#test-1, #test-2').attr('data-test', 'intermediary state');
  
  $('#test-1').attr('data-test', t1);
  $('#test-2').attr('data-test', t2);
  
  console.assert(!$('#test-1').is('[data-test]'), 'Passing the original value of [data-test] should return #test-1 to its original state.');
  console.assert($('#test-2').is('[data-test]'), 'Passing the original value of [data-test] should return #test-2 to its original state.');
}());