JSFiddle - React, Tailwind, and code Playground

HTML

<div title="a.b[c"></div>
<div id="result"></div>
<div id="expected">11</div>

JavaScript

$('#result')
    .append($('div[title="a\\.b\\[c"]').length)
    .append($('div[title="a\\.b\\[c"]:first').length);