window.open in a callback

window.open.js

//Do this first!
window.open("about:blank", "sharer");

var params = {...}
ajaxFunction(function (data) {

    var url = 'http://google.ca';
    //Refer to the original window here...
    var w = window.open(url, 'sharer');
    return (!w); // opens in new window/tab if allowed

}, params);