Create context for another site collection using NAPA

I am trying to access another site collection using NAPA. I found 2 ways, none of which seem to be working

Office 365- Accessing lists refers wrong URL (URL/App name)

var context = new SP.AppContextSite(SP.ClientContext.get_current(), 'https://URL/sites/DevSite/');

The code stops at this line.

http://ift.tt/1xeQR8K

$(document).ready(function () {

var appWebUrl1 = decodeURIComponent(getQueryStringParameter("SPAppWebUrl"));
    var hostWebUrl1 = decodeURIComponent(getQueryStringParameter("SPHostUrl")); var factory;

    this.context = new SP.ClientContext(appWebUrl1);
    factory = new SP.ProxyWebRequestExecutorFactory(appWebUrl1);
    this.context.set_webRequestExecutorFactory(factory);
    this.hostContext = new SP.AppContextSite(context, hostWebUrl1);

getQueryStringParameter is underlined in red as "undefined"