spcontext.js without jquery

spcontext.js

/*!spcontext*/
(function (window, undefined) {

    "use strict";

    //var $ = window.jQuery;
    var document = window.document;

    // SPHostUrl parameter name
    var SPHostUrlKey = "SPHostUrl";

    // Gets SPHostUrl from the current URL and appends it as query string to the links which point to current domain in the page.
    //$(document).ready(function () {
    ensureSPHasRedirectedToSharePointRemoved();

    var spHostUrl = getSPHostUrlFromQueryString(window.location.search);
    var currentAuthority = getAuthorityFromUrl(window.location.href).toUpperCase();

    if (spHostUrl && currentAuthority) {
        appendSPHostUrlToLinks(spHostUrl, currentAuthority);
    }
    //});

    // Appends SPHostUrl as query string to all the links which point to current domain.
    function appendSPHostUrlToLinks(spHostUrl, currentAuthority) {
        //$("a").filter().each();

        var elements = Array.prototype.filter.call(document.querySelectorAll('a'), function (el,i) {
            var authority = getAuthorityFromUrl(el.href);
            if (!authority && /^#|:/.test(el.href)) {
                // Filters out anchors and urls with other unsupported protocols.
                return false;
            }
            return authority.toUpperCase() == currentAuthority;
        });

        Array.prototype.forEach.call(elements, function (el, i) {
            if (!getSPHostUrlFromQueryString(el.search)) {
                if (el.search.length > 0) {
                    el.search += "&" + SPHostUrlKey + "=" + spHostUrl;
                }
                else {
                    el.search = "?" + SPHostUrlKey + "=" + spHostUrl;
                }
            }
        });

    }

    // Gets SPHostUrl from the given query string.
    function getSPHostUrlFromQueryString(queryString) {
        if (queryString) {
            if (queryString[0] === "?") {
                queryString = queryString.substring(1);
            }

            var keyValuePairArray = queryString.split("&");

            for (var i = 0; i < keyValuePairArray.length; i++) {
                var currentKeyValuePair = keyValuePairArray[i].split("=");

                if (currentKeyValuePair.length > 1 && currentKeyValuePair[0] == SPHostUrlKey) {
                    return currentKeyValuePair[1];
                }
            }
        }

        return null;
    }

    // Gets authority from the given url when it is an absolute url with http/https protocol or a protocol relative url.
    function getAuthorityFromUrl(url) {
        if (url) {
            var match = /^(?:https:\/\/|http:\/\/|\/\/)([^\/\?#]+)(?:\/|#|$|\?)/i.exec(url);
            if (match) {
                return match[1];
            }
        }
        return null;
    }

    // If SPHasRedirectedToSharePoint exists in the query string, remove it.
    // Hence, when user bookmarks the url, SPHasRedirectedToSharePoint will not be included.
    // Note that modifying window.location.search will cause an additional request to server.
    function ensureSPHasRedirectedToSharePointRemoved() {
        var SPHasRedirectedToSharePointParam = "&SPHasRedirectedToSharePoint=1";

        var queryString = window.location.search;

        if (queryString.indexOf(SPHasRedirectedToSharePointParam) >= 0) {
            window.location.search = queryString.replace(SPHasRedirectedToSharePointParam, "");
        }
    }

})(window);