Accurately returns the height and width of the viewport much more reliably than $(window).height

viewport.js

/*
 * Accurately returns the height and width of the viewport
 * much more reliably than simply $(window).height
 *
 * Source: http://andylangton.co.uk/blog/development/get-viewport-size-width-and-height-javascript
 */

function viewport() {
  var e = window, a = 'inner';

  if ( !( 'innerWidth' in window ) ) {
    a = 'client';
    e = document.documentElement || document.body;
  }

  return { width : e[ a+'Width' ] , height : e[ a+'Height' ] }
}

function is_mobile() {
  if (viewport().width < 768) {
    return true;
  } else {
    return false;
  }
}