JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://code.jquery.com/jquery-1.9.1.min.js"></script>
<form method="POST">
<button type="submit">
BTN
</button>
</form>
<a href="http://google.com.vn">Click a</a>

JavaScript

$("button, a").on("click", function(){
    window.is_clicked= true;
});

window.onbeforeunload = function(){
    if(window.is_clicked){
        return 'Leave?.';
    }
};