helpers.js

module.exports = {

  // opens a centered popup window
  openWindow: function(url, width, height) {
    var left = screen.width / 2 - width / 2;
    var top = screen.height / 2 - height / 2;

    window.open(
      url,
      '',
      'width=' + width + ',height=' + height + ', top=' + top + ', left=' + left
    );
  }
};

share.js

import H from '../globals/helpers';

var Share = function(elem) {
  this.elem = elem;
  this.init();
};

Share.prototype = {
  init: function() {
    this.bindEvents();
  },

  bindEvents: function() {
    this.elem.addEventListener(
      'click',
      this.elem.getAttribute('data-js') === 'share'
        ? this.shareIt
        : this.printIt
    );
  },

  shareIt: function(event) {
    event.preventDefault();
    H.openWindow(this.getAttribute('href'), 630, 265);
  },

  printIt: function() {
    window.print();
  }
};

module.exports = Share;

share.twig

<ul class="share__list">
  <li class="share__item">
    <a
      class="svg-icon svg-icon--facebook"
      data-js="share"
      href="https://www.facebook.com/sharer/sharer.php?u={{ post.link }}">
      <span class="sr-only">Share on Facebook</span>
    </a>
  </li>
  <li class="share__item">
    <a
      class="svg-icon svg-icon--twitter"
      data-js="share"
      href="https://twitter.com/share?url={{post.link}}&amp;text={{post.title}}&amp;via=atlantic">
      <span class="sr-only">Tweet this Page</span>
    </a>
  </li>
  <li class="share__item">
    <a
      class="svg-icon svg-icon--email"
      href="mailto:?subject={{"#{post.title} | The Atlantic Philanthropies"|url_encode}}&amp;body={{ "#{post.link}

- Sent via The Atlantic Philanthropies"|url_encode }}">
      <span class="sr-only">Email Page</span>
    </a>
  </li>
  <li class="share__item">
    <button
      class="svg-icon svg-icon--print"
      data-js="print">
      <span class="sr-only">Print this Page</span>
    </button>
  </li>
</ul>