Problem with asyncronous calls

Problem and how to solve with closure

function tryIt() {
	var sheets = {
		"1": {
			"name": "type1",
			"marker": "http://www.google.com/mapfiles/markerA.png"
		},
		"2": {
			"name": "type2",
			"marker": "http://www.google.com/mapfiles/markerB.png"
		},
		"3": {
			"name": "type3",
			"marker": "http://www.google.com/mapfiles/markerC.png"
		},
		"4": {
			"name": "type4",
			"marker": "http://www.google.com/mapfiles/markerD.png"
		},
		"5": {
			"name": "type5",
			"marker": "http://www.google.com/mapfiles/markerE.png"
		},
		"6": {
			"name": "type6",
			"marker": "http://www.google.com/mapfiles/markerF.png"
		},
		"7": {
			"name": "type7",
			"marker": "http://www.google.com/mapfiles/markerG.png"
		}
	};
	window.sheets=sheets;
	var url = "http://localhost:3000/";
	for (var key in sheets) {
		console.log(sheets[key].marker)

		$.ajax({
			type: "GET",
			url: url + "?key=" + key,
			success: function(data) {
				loadMarker(key, data);
			},
			error: function() {
				console.log("Are you sure you are connected to the internet?");
			}
		});
	}

	function loadMarker(key, data) {
		//URL: http://www.google.com/mapfiles/markerG.png?token=*SomeToken*
		console.log("Final url:"+ sheets[key].marker+"?token="+data.token)
		sheets[key].finalURL=sheets[key].marker+"?token="+data.token;
	}
}

//related nodejs code:

var express = require('express');
var app = express();

app.get('/', function (req, res) {
res.header("Access-Control-Allow-Origin", "");
res.header("Access-Control-Allow-Headers", "X-Requested-With");
res.json({"token":req.query*77});
});

app.listen(3000, function () {
console.log('Example app listening on port 3000!');
});