JSFiddle - React, Tailwind, and code Playground

HTML

<div id="result"></div>

JavaScript

var result1 = 0;
for (var i = 1; i <= 100; i++) {  // count up
    result1 += 1/Math.pow(3, i);
}

var result2 = 0;
for (var i = 100; i >= 1; i--) {  // count down
    result2 += 1/Math.pow(3, i);
}

document.getElementById("result").innerHTML = "" + result1 + "<br>" + result2;