JSFiddle - React, Tailwind, and code Playground

CSS

body { font-family: sans-serif; }

JavaScript

var timeString = "18:00:00";
var H = +timeString.substr(0, 2);
var h = (H % 12) || 12;
var ampm = H < 12 ? "AM" : "PM";
timeString = h + timeString.substr(2, 3) + ampm;
document.write(timeString);