Comments on: Never worry about ASP.NET AJAX’s .d again

By: Dave Ward

Dave Ward — Tue, 15 May 2012 19:04:49 +0000

That's easy to say now that you're much more likely to be primarily targeting browsers that support native JSON.parse. At the time this was written, native JSON.parse was a relatively new feature. jQuery itself still used eval() to deserialize all JSON responses at this time, even if the browser did have native JSON.parse support (in fact, my next post on this topic discussed extending this approach to use native JSON.parse when available). For that matter, even Crockford's json2.js uses eval() in its implementation of JSON.parse (after a bit of input sanitizing). There were parse-only implementations floating around, but it turned out to be prohibitively slow in the older JavaScript engines that need JSON.parse polyfilled. I suppose what I'm saying is that you have to be careful about making blanket statements about eval(); especially in historical context. "Eval is evil" comes from Crockford, but his own acceptance of eval() for JSON evaluation played a critical role in JSON being a viable format in the first place.

By: Chris Hoffman

Chris Hoffman — Thu, 10 May 2012 16:38:59 +0000

Use JSON.parse instead of eval everywhere, always. Encouraging any use of eval promotes bad programming practices.

By: Dave Ward

Dave Ward — Mon, 30 Apr 2012 18:03:33 +0000

Working with ASMX “ScriptServices” and ASPX page methods, there’s no much choice, because you’ll always be POSTing and the .d is added at the framework level.

It might make sense to manually add something like this to sensitive GET-able endpoints under MVC or Web API though.

By: Jason Day

Jason Day — Thu, 26 Apr 2012 18:19:20 +0000

I’m assuming this same technique can be used with a GET and instead of the .d, a cruft such as “for(;;)” or “while(1);” ?

By: Using jQuery in ASP.NET applications – part 1 Web Forms | Bart De Meyer – Blog

Tue, 21 Feb 2012 15:14:45 +0000

[...] return message is wrapped in a “d” variable. This is changed in the .NET 3.5 version. More info in Dave Ward’s post on Encosia. After that we create an option to be added in the listbox and append it to this [...]

By: Dave Ward

Dave Ward — Sun, 19 Feb 2012 19:10:21 +0000

Just keep in mind that the extra overhead from the redundant stringify and $.parseJSON will become significant on larger responses, which can lead to visible stutters in your interface since JavaScript and the browser's rendering engine run together in a single thread.

By: Terry

Terry — Tue, 14 Feb 2012 17:45:36 +0000

If all your AJAX calls are using ASP.NET 3.5, the following will work:

    $.ajaxSetup({
        dataFilter: function (data) {
            return JSON.stringify($.parseJSON(data).d);            
        }
    });

By: nerd

nerd — Tue, 31 May 2011 16:39:50 +0000

you right, but i think that return just a value there is a bad practice or bad use of JSON cause if we are talking about JSON (JavaScript Object Notation) responses, return a lonely value is the mistake (even if in javascript everything is an object).

You right, but if programmers do not understand what JSON it is then we should correct to teach the right way.

Regards!

By: Dave Ward

Dave Ward — Tue, 31 May 2011 16:23:52 +0000

People often return scalar values from their methods (which is valid JSON with the .d wrapper). A boolean indicating success/failure of an update is common, for example. If that method returns false, the ternary approach would pass
{ d: false } back through the dataFilter instead of false. Same issue with any methods that might return 0 or an empty string. If you're never returning anything but an object, the ternary should be safe, yes.

By: nerd

nerd — Tue, 31 May 2011 16:17:25 +0000

but if you return valid json structures there is no way that the value could be an unexpected ‘false’ or ‘null’, actually i use this code in almost 6 applications in different servers and different .Net frameworks and i don’t get any error, when you return a json object you know the sctructure and possible values, so you shouldn’t get any surprise.

By: Dave Ward

Dave Ward — Tue, 31 May 2011 16:09:39 +0000

You would run into trouble there if the return value was intentionally the value false or something ambiguously falsy like the number 0 or null.

By: nerd

nerd — Tue, 31 May 2011 16:07:03 +0000

actually, can be converted to:

data = data.d ? data.d : data;

By: A quick guide to have jQuery call your ASP.NET PageMethods « I Came, I Learned, I Blogged

Sat, 21 May 2011 15:15:58 +0000

[...] be the case, although a more complex solution for checking if a ‘d’ is there already exists. Anyway, the proposed solution simply takes a JSON string returned from from the server, parses it [...]

By: ASP.NET, AJAX i JSON « Asp.net « Web Development « Pure Development Blog

Sun, 08 May 2011 00:09:27 +0000

[...] Never worry about ASP.NET AJAX’s .d again [...]

By: Robin Herbots

Robin Herbots — Mon, 18 Apr 2011 11:27:29 +0000

As from Jquery 1.5 I use the following to solve the .d

converters: {
// Evaluate text as a json expression
“text json”: function(data) {
var dataObj = $.parseJSON(data);
return dataObj.hasOwnProperty(‘d’) ? dataObj.d : dataObj;
}
}