Retrieve Url Parameter Values.

encodeHTML.js

function encodeHTML(s) {
    return s.replace(/&/g, '&amp;').replace(/</g, '&lt;').replace(/"/g, '&quot;');
}

ifPage.js

function ifPage(url, fx) {
	if (window.location.pathname.slice(0, -5) == url) { // trailing ".html"
		fx();
	} else if (window.location.pathname == url) {
		fx();
	}
}

paramVal.js

function paramVal(param) {
    param = param.replace(/[\[\]]/g, "\\$&");
    var regex = new RegExp("[?&]" + param + "(=([^&#]*)|&|#|$)"),
        results = regex.exec(window.location.href);
    if (!results) return null;
    if (!results[2]) return '';
    return decodeURIComponent(results[2].replace(/\+/g, " "));
}

// url -> https://www.example.com/?ref=facebook
// code -> paramVal("ref") returns "facebook"