JSFiddle - React, Tailwind, and code Playground

HTML

<script src="http://converter.creeation.de/bignumber.min.js"></script>
<div>
    <form>
        <input type="text" name="id" placeholder="STEAM / COMMUNITY ID" />
        <input type="submit" value=">" />
    </form>
</div>

JavaScript

$(function() {

				var id, server_id, account_id, community_id_start = '76561197960265728';

				Number.prototype.mod = function(n) {
					return ((this%n)+n)%n;
				}

				function getCommunityID(id) {

					var com_id = id.replace( 'STEAM_', '' );
					com_id = com_id.split( ':' );

					if ( com_id.length == 3 ) {

						server_id = com_id[1];
						account_id = com_id[2];

						com_id = new BigNumber( account_id * 2 ).add(community_id_start).add(server_id).toString();

					}

					return com_id;

				}

				function getSteamID(id) {

					var a = new BigNumber(id).subtract(community_id_start).divide(2);
					var b = Math.floor( a );
					var c = Math.round( a % b );

					id = '0:' + c + ':' + b;

					return id;

				}

				$('form').on('submit', function(e) {
					var LOL = $('input[type="text"]', this).val();
					var OMG = getCommunityID(LOL);
					$(this).append(OMG);
					var ROFL = getSteamID(OMG);
					$(this).append('<br>' + ROFL);

					e.preventDefault();
				});

			});