JSFiddle - React, Tailwind, and code Playground

HTML

<button onclick="alert(notAClosure());">notAClosure</button>
<button onclick="alert(checkLocalX);">testClosure</button>

JavaScript

function notAClosure(){
    var x = 4;
    return x;
}
function testClosure(){
    var x = 5;
    function closeX(){
        return x;
    }
    return closeX();
}
    var checkLocalX = testClosure();