Question

What would be the prefered way to initialize a JS array in ASP.NET MVC 3 with Razor with a value I have in my model/view model ?

For example to initialize an array of strings representing dates :

<script type="text/javascript">
    var activeDates = ["7-21-2011", "7-22-2011"];
</script>

with

public class MyViewModel
{    
  public DateTime[] ActiveDates { get; set; }
}

Answer 1

I don’t quite understand the relation between JS and ASP.NET MVC 3 Razor. Javascript runs on the client side no matter which technology has been used on the server to generate the page. So on javascript an array is an array.

There are a couple of possibilities to define arrays of objects in javascript

var activeDates = [ '7-21-2011', '7-22-2011' ];

or:

var activeDates = new Array();
activeArrays.push('7-21-2011');
activeArrays.push('7-22-2011');

or yet:

var activeDates = new Array();
activeArrays[0] = '7-21-2011';
activeArrays[1] = '7-22-2011';

At th end all those represent the same array. But it is an array of strings, not dates.

If you wanted to have an array of dates, here’s what you could do:

var activeDates = [ 
    new Date(2011, 6, 21, 0, 0, 0, 0), 
    new Date(2011, 6, 22, 0, 0, 0, 0) 
];

Now the only relation I can see with your question to ASP.NET MVC is that you probably have some array on your view model:

public class MyViewModel
{
    public DateTime[] ActiveDates { get; set; }
}

that you wanted to serialize and manipulate in a javascript array. In this case here’s the syntax:

@model MyViewModel
<script type="text/javascript">
    var activeDates = @Html.Raw(Json.Encode(Model.ActiveDates));
</script>

Now because of the way DateTime fields are JSON serialized in .NET you will end up with the following in the generated HTML:

var activeDates = ["\/Date(1309471200000)\/","\/Date(1311199200000)\/"];

and if you wanted to convert this array of strings into an array of actual javascript dates:

var dates = $.map(activeDates, function(date, index) {
    date = date.replace('/Date(', '').replace(')/', '');  
    return new Date(parseInt(date));
});