JSFiddle - React, Tailwind, and code Playground

HTML

<input type="checkbox">
<input type="checkbox">
<input type="checkbox">
<input type="checkbox">
<input type="checkbox">
<input type="checkbox">
<input type="checkbox">
<input type="checkbox">
<input type="checkbox">
<input type="checkbox">

JavaScript

var cb = document.querySelectorAll("[type=checkbox]");

var i = 0,
	  l = cb.length;

for (; i<l; i++)
	cb[i].addEventListener("change", function (){
		if (document.querySelectorAll(":checked").length > 5)
			this.checked = false;
	}, false);