Question: I have this code : 

```
var mapcity = new Array([]);              

         $.ajax({
             type: 'GET',
             url: '/home/DrawMap',
             dataType: 'json',
             success: function (data) {

                 var len = data.length;

                 for (var i = 0; i < len; i++) {

                    // mapcity['' + data[i].name + ''] = { center: new google.maps.LatLng(data[i].x, data[i].y), population: data[i].population, name: '' + data[i].name + '' };
                     mapcity['' + data[i].name + ''] = { center: new google.maps.LatLng(data[i].x, data[i].y), population: data[i].population, name: ''+data[i].name+'' };
                     //newarr[i] = data[i].name;

                   alert(mapcity[0].population)
                 }
                 }
         });
}

```

This is a part of my code, and this is the function from controller :

```
public ActionResult DrawMap() {   

  string data = "[{ 'x':31.949454,'y': 35.932913,'population':50000,'name':'amman'},{ 'x':33.79,'y': 33.39,'population':100000,'name':'Zarqa'}]";
        data=data.Replace("'","\"");
        return this.Content(data, "application/json");       

    }

```

When I run this, its het the JSON data from the controller but without saving it into the mapcity variable!
And it does nothing. how can I solve it and what iam doing wrong?

Answer: 
You should never be manually building JSON as you did but always use a JSON serializer:

```
public ActionResult DrawMap() 
{
    var data = new[]
    {
        new
        {
            x = 31.949454,
            y = 35.932913,
            population = 50000,
            name = "amman",
        },
        new
        {
            x = 33.79,
            y = 33.39,
            population = 100000,
            name = "Zarqa",
        }
    };

    return Json(data, JsonRequestBehavior.AllowGet);
}

```

Also you have declared your `mapcity` variable outside of the success handler which is leading me into thinking that you are attempting to use its value immediately after the $.ajax call which obviously is not possible because AJAX by its very own nature is asynchronous. This means that the success callback could be executed much later and the $.ajax call returns immediately.

So the only single safe place to use this variable is **INSIDE** the success function:

```
$.ajax({
    type: 'GET',
    url: '/home/DrawMap',
    success: function (data) {
        var mapcity = {};
        var len = data.length;
        for (var i = 0; i < len; i++) {
            mapcity['' + data[i].name + ''] = { center: new google.maps.LatLng(data[i].x, data[i].y), population: data[i].population, name: ''+data[i].name+'' };
        }
    }
});

```

You also have another problem. You declared `mapcity` variable as array (`new Array([])`) and then you attempted to insert non-integer indexes into it:

```
mapcity['' + data[i].name + '']

```

In javascript when you declare an array, it can only have 0 based integer indexes. So you could either declare it as a javascript object var `mapcity = {};` or use integer indexes only.
Easiest way:

Your array of strings:

```
var data;
data.push('string1');
data.push('string2');

var jData = JSON.stringify(data); // convert to Json string

$.ajax({
    type: "POST",
    traditional: true,
    dataType: 'json',
    contentType: "application/json; charset=utf-8",
    url: "/Controller/MethodName",
    data: jData ,
    success: function (result) {
       if (result) {
       }
    }
});

```

Controller:

```
public ActionResult MethodName(List<String> jData )
{
   ....
   return Json(yourResult);
}

```