promises thing

gistfile1.js

initMap = function(){
    var self = this;
    return $.Deferred(function(dfd){
        if(self.mapLoaded){
            // Map is loaded y'all.
            dfd.resolve();
        }
        else{
            $.ajax( // load your thing)
            .done(function(){
                // Map loaded correctly? Set our mapLoaded flag and resolve our promise
                self.mapLoaded = true;
                dfd.resolve();
            });
        }
    }).promise();
}

// ... and then
$.when(this.initMap())
    .done(function(){ 
        // Maps are loaded! This will either execute after your Ajax request 
        // if the map isn't loaded or immediately if the map is already loaded.
    });