JSFiddle - React, Tailwind, and code Playground

HTML

<div id="a.b">a.b</div>
<div id="a#b">a#b</div>
<div id="a" class="b">a.b</div>

CSS

#a\.b {
  color: red;
}

#a\#b {
  color: blue;
}
#a.b {
  color: green;
}