javascript - Handling dates with Asp.Net MVC and KnockoutJS

Question

I recently started working with KnockoutJs and quickly realized using the default Json(myModelWithADate) resulted in the default json encoding of /Date(-62135578800000)/ With a bit of research I located four potential ways to handle the display of my dates in dom elements.

1) Create a binding that handles the conversion from the Json date to the format you desire

ko.bindingHandlers.date = {
    init: function (element, valueAccessor, allBindingsAccessor, viewModel) {
        var jsonDate = valueAccessor();
        var value = new Date(parseInt(jsonDate.substr(6)));
        var ret = value.getMonth() + 1 + "/" + value.getDate() + "/" + value.getFullYear();
        element.innerHTML = ret;
    },
    update: function(element, valueAccessor, allBindingsAccessor, viewModel) {

    }
};

Usage

<td data-bind="date: DueDate">
</td>

2) Return “strings” from your Controller

return Json(new {MyDate = DateTime.Now.ToShortDateString()});

3) Use the JSON.NET to specify a Date Time format seen over at james.newtonking.com

Example

string isoJson = JsonConvert.SerializeObject(entry, new IsoDateTimeConverter());
// {"Details":"Application started.","LogDate":"2009-02-15T00:00:00Z"}

4) use JSON.parse to handle your dates as seen in this stackoverflow answer.

JSON.parse(jsonText, function(key, value) {
    // Check for the /Date(x)/ pattern
    var match = //Date((d+))//.exec(value);
    if (match) {
        var date = new Date(+match[1]); // Convert the ticks to a Date object
        return humanReadable(date); // Format the date how you want it
    }

    // Not a date, so return the original value
    return value;
});

They all appear to work, but I am still struggling with which one feels “right”. Right now my gut is going with a mix with the binding and returning strings. As I could see myself extending the binding to handle input with jQuery UI datepicker controls.

Is there an accepted practice when handling displaying dates or other types such as currency? Is there another option I am missing that solves this problem?

Answer 1

Personally I think the JSON.NET solution is the best simply because it imposes less on the client. All the other solutions require additional client parsing or additional client code.

I have switched over to using JSON.NET for all of my ASP .NET code that uses JSON because its a much more customizable library.

For example I have had to implement JSON data in MVC that conformed to Google's Chart API (used in combination with Knockout for paging, etc.) and the default JavascriptSerializer simply cannot do it.

In addition with JSON.NET you can customize it to actually spit out full Knockout view models so you don't even need to employ the mapping plugin.

I wrote a sample library called FluentJson.NET which lets you do things in Razor like:

var viewModel = @JsonObject.Create()
    .AddProperty("name", "value")
    .AddObservable("knockoutProperty", 123)

And get:

var viewModel = {"name":"value","knockoutProperty":ko.observable(123)}

So you can get a Knockout view model without any client side hoops to jump through.

You could easily extend something like that to handle date values however you would prefer.