JSFiddle - React, Tailwind, and code Playground

HTML

<div data-Lon1="1.3" data-Lat1="-1.2"></div>

JavaScript

var lon1 = $('div').data('lon1');
var lat1 = $('div').data('lat1');
console.log( Math.round( ( lat1+lon1 ) * 100000000000 ) / 100000000000 );