A small helper, which detects orientation of viewport. Sets 'is-landscape' or 'is-portrait' to the html element.

detect-orientation.js

'use strict';

(function(){
    window.NIJS = window.NIJS || {};
    NIJS.detection = NIJS.detection || {};

    var html = document.getElementsByTagName('html')[0],

        removeClass = function(str, className){
            var classArr = str.split(' '),
                index = -1;

            for(var i = classArr.length; i--; ) {
                if(classArr[i] == className){
                    index = i;
                    break;
                }
            }

            if(index > -1) {
                classArr.splice(index, 1);
            }

            return classArr.join(' ');
        };

    function detectOrientation(){
        html.className = removeClass(html.className, 'is-landscape');
        html.className = removeClass(html.className, 'is-portrait');

        if(window.innerHeight > window.innerWidth){

            // is portrait
            html.className += ' is-portrait';
            NIJS.detection.orientation = 'portrait';

        }else {

            // is landscape
            html.className += ' is-landscape';
            NIJS.detection.orientation = 'landscape';
        }
    }

    window.addEventListener('resize', detectOrientation);

    // set initial value
    detectOrientation();
})();