JSFiddle - React, Tailwind, and code Playground

HTML

<div class="container">
	<br><br>
	<a href="http://www.google.com" class="button">Proceed</a>		
	<br><br>
	<div class="price">$139.99</div>
	<br><br>
	<span></span>
</div>

JavaScript

// function
priceFunction = function (){
	window.onbeforeunload = function() {
			return 'Sure you want to leave?';
	}
};

// if price is 139.99, run function
var price = $(".price").text().replace(/[^0-9\.]/g, '');
if (price = 139.99){
	priceFunction();
}