JSFiddle - React, Tailwind, and code Playground
HTML
<input type="text" name="foo[front]" />
<input type="text" name="foo[front]" />
<input type="text" name="bar[front]" />
JavaScript
console.log($('[name^=foo]').filter('[name=foo\\[front\\]]').length);
console.log($('[name^=bar]').filter('[name=bar\\[front\\]]').length);