JSFiddle - React, Tailwind, and code Playground

by Michael Wang

HTML

Result: <span id="result"></span>

JavaScript

var s = '/Date(1399739515000)/';
var r = /\/Date\((\d*?)\)\//.exec(s);
var d = new Date(parseInt(r[1]));
document.getElementById('result').innerHTML = d.getFullYear() + '-' + d.getMonth() + '-' + d.getDate() + ' ' + d.getHours() + ':' + d.getMinutes() + ':' + d.getSeconds();