JSFiddle - React, Tailwind, and code Playground

HTML

<p>Name: <span id="pName"></span></p>
<p>Age: <span id="pAge"></span></p>

CSS

body {
    font-size: 30px;
}
.fresh {
    color: green;
}
.old {
    color: red;
}

JavaScript

var person = {
    name: "John Doe",
    age: 25
};
var tagName = document.getElementById("pName");
tagName.innerHTML = person.name;
var tagAge = document.getElementById("pAge");
tagAge.innerHTML = person.age;
if (person.age < 18) {
    tagAge.className = "fresh";
} else if (person.age > 65) {
    tagAge.className = "old";
}