JSFiddle - React, Tailwind, and code Playground

HTML

<body>
    <button type="button" onClick="John()">I AM BUTTON</button>
</body>

JavaScript

/* Retirement Age is set to 65 */
function people(name, age) {
    this.name = name;
    this.age = age;
    this.YearsUntilRetire = RetireLeft;
}

function RetireLeft() {
    var NumRetire = 65 - this.age;
    return NumRetire;
}
var SomeDude = new people("John Doe", 51);

function John() {
    alert(SomeDude.YearsUntilRetire());
}
// Sorry, this works in Notepad++, don't know why it doesn't in fiddle.