Edit in JSFiddle

function getOrigin(url) {
  if (!url) {
    return null;
  } else {
    var matched = url.match(/^([a-zA-Z]+:\/\/.[^/]+).*/);
    return (matched.length > 1) ? matched[1] : null;
  }
}

var url = 'https://twitter.com/yurenju/status/402368329135816704';

document.getElementById('msg1').innerHTML = getOrigin(url);

var urlObj = new URL(url);
document.getElementById('msg2').innerHTML = urlObj.origin;

<div id="msg1"></div>
<div id="msg2"></div>