Using JavaScript to open links (not within the host site) in a new tab

new-tab.js

// Adds attribute "target=_blank" to links to all external sites
function handleExternalLinks () {
  var host = location.host
  var allLinks = document.querySelectorAll('a')
  forEach(allLinks, function (elem, index) {
    checkExternalLink(elem, host)
  })
}

function checkExternalLink (item, hostname) {
  var href = item.href
  var itemHost = href.replace(/https?:\/\/([^\/]+)(.*)/, '$1')
  if (itemHost !== '' && itemHost !== hostname) {
    item.target = '_blank'
  }
}

// NodeList forEach function
function forEach (array, callback, scope) {
  for (var i = 0; i < array.length; ++i) {
    callback.call(scope, array[i], i)
  }
}