Use application/javascript. In that way, clients can rely on the content-type without having to manually check whether a response has padding or not.

Use `application/json` [as per rfc4627.txt][1] if what you return is plain JSON.

If you return JavaScript (which is really what JSONP is), then use `application/javascript` [as per rfc4329.txt][2] 

  [1]: http://www.ietf.org/rfc/rfc4627.txt
  [2]: http://www.rfc-editor.org/rfc/rfc4329.txt

I know what Hungarian refers to - giving information about a variable, parameter, or type as a prefix to its name. Everyone seems to be rabidly against it, even though in some cases it seems to be a good idea. If I feel that useful information is being imparted, why shouldn&#39;t I put it right there where it&#39;s available?

See also: [Do people use the Hungarian naming conventions in the real world?][1] 

  [1]: https://stackoverflow.com/questions/5428/do-people-use-the-hungarian-naming-conventions-in-the-real-world

Why shouldn&#39;t I use &quot;Hungarian Notation&quot;?

C++ is all about memory ownership - aka **ownership semantics**.

It is the responsibility of the owner of a chunk of dynamically allocated memory to release that memory. So the question really becomes who owns the memory.

In C++ ownership is documented by the type a *raw* pointer is wrapped inside thus in a good (IMO) C++ program it is very rare (*rare*, not *never*) to see raw pointers passed around (as raw pointers have no inferred ownership thus we can not tell who owns the memory and thus without careful reading of the documentation you can&#39;t tell who is responsible for ownership).

Conversely, it is rare to see raw pointers stored in a class each raw pointer is stored within its own smart pointer wrapper. (**N.B.:** If you don&#39;t own an object you should not be storing it because you can not know when it will go out of scope and be destroyed.)

So the question:

- What type of ownership semantic have people come across?
- What standard classes are used to implement those semantics?
- In what situations do you find them useful?

Lets keep 1 type of semantic ownership per answer so they can be voted up and down individually.

## Summary:

Conceptually, smart pointers are simple and a naive implementation is easy. I have seen many attempted implementations, but invariably they are broken in some way that is not obvious to casual use and examples. Thus I recommend always using well tested smart pointers from a library rather than rolling your own. `std::auto_ptr` or one of the Boost smart pointers seem to cover all my needs.


### `std::auto_ptr&lt;T&gt;`:

  Single person owns the object. Transfer of ownership is allowed.

  Usage: This allows you to define interfaces that show the explicit transfer of ownership.

### `boost::scoped_ptr&lt;T&gt;`

  Single person owns the object. Transfer of ownership is NOT allowed.

  Usage: Used to show explicit ownership. Object will be destroyed by destructor or when explicitly reset.

### `boost::shared_ptr&lt;T&gt;` (`std::tr1::shared_ptr&lt;T&gt;`)

  Multiple ownership. This is a simple reference counted pointer. When the reference count reaches zero, the object is destroyed.

  Usage: When an object can have multiple owers with a lifetime that can not be determined at compile time.

### `boost::weak_ptr&lt;T&gt;`:

  Used with `shared_ptr&lt;T&gt;` in situations where a cycle of pointers may happen.

  Usage: Used to stop cycles from retaining objects when only the cycle is maintaining a shared refcount.


Smart pointers: who owns the object?

I have a webservice that when called without specifying a callback will return a JSON string using &lt;code&gt;application/json&lt;/code&gt; as the content type.

When a callback is specified it will wrap the JSON string in a callback function, so it&#39;s not really valid JSON anymore. My question is, should I serve it as &lt;code&gt;application/javascript&lt;/code&gt; in this case or still use &lt;code&gt;application/json&lt;/code&gt;?

Best content type to serve JSONP?

<p>I have a webservice that when called without specifying a callback will return a JSON string using <code>application/json</code> as the content type.</p>
<p>When a callback is specified it will wrap the JSON string in a callback function, so it's not really valid JSON anymore. My question is, should I serve it as <code>application/javascript</code> in this case or still use <code>application/json</code>?</p>


CPU Cycles, Memory Usage, Execution Time, etc.?

Added: Is there a quantitative way of testing performance in JavaScript besides just perception of how fast the code runs?


How do you performance test JavaScript code?

Is there any way to create the _query parameters_ for doing a _GET request_ in JavaScript?

Just like in Python you have [`urllib.urlencode()`][1], which takes in a dictionary (or list of two tuples) and creates a string like `&#39;var1=value1&amp;var2=value2&#39;`.

  [1]: http://web.archive.org/web/20080926234926/http://docs.python.org:80/lib/module-urllib.html

How to create query parameters in Javascript?

On my team, we usually do string concatentation like this:

    var url = // some dynamically generated URL
    var sb = new StringBuffer();
    sb.append(&quot;&lt;a href=&#39;&quot;).append(url).append(&quot;&#39;&gt;click here&lt;/a&gt;&quot;);

Obviously the following is much more readable:

    var url = // some dynamically generated URL
    var sb = &quot;&lt;a href=&#39;&quot; + url + &quot;&#39;&gt;click here&lt;/a&gt;&quot;;

But the JS experts claim that the `+` operator is less performant than `StringBuffer.append()`. Is this really true?


is the + operator less performant than StringBuffer.append()

I don’t think I’ve grokked currying yet. I understand what it does, and how to do it. I just can’t think of a situation I would use it.

Where are you using currying in JavaScript (or where are the main libraries using it)? DOM manipulation or general application development examples welcome.

[One of the answers][1] mentions animation. Functions like `slideUp`, `fadeIn` take an element as an arguments and are normally a curried function returning the high order function with the default “animation function” built-in. Why is that better than just applying the higher-up function with some defaults?

Are there any drawbacks to using it?

As requested here are some good resources on JavaScript currying:

  - [http://www.dustindiaz.com/javascript-curry/][2]
  - Crockford, Douglas (2008) *JavaScript: The Good Parts*
  - [http://www.svendtofte.com/code/curried_javascript/][3]
 (Takes a detour into ML so skip the whole section from “A crash course in ML” and start again at “How to write curried JavaScript”)
  - [http://web.archive.org/web/20111217011630/http://blog.morrisjohns.com:80/javascript_closures_for_dummies][4]
  - [https://stackoverflow.com/questions/111102/how-does-a-javascript-closure-work][5]
  - **[http://ejohn.org/blog/partial-functions-in-javascript][6] (Mr. Resig on the money as per usual)**
  - &lt;http://benalman.com/news/2010/09/partial-application-in-javascript/&gt;

I’ll add more as they crop up in the comments.

---

So, according to the answers, currying and partial application in general are convenience techniques.

If you are frequently “refining” a high-level function by calling it with same configuration, you can curry (or use Resig’s partial) the higher-level function to create simple, concise helper methods.


  [1]: https://stackoverflow.com/questions/113780/javascript-curry-what-are-the-practical-applications#113799
  [2]: http://www.dustindiaz.com/javascript-curry/
  [3]: http://www.crockford.com/javascript/www_svendtofte_com/code/curried_javascript/index.html
  [4]: http://web.archive.org/web/20111217011630/http://blog.morrisjohns.com:80/javascript_closures_for_dummies
  [5]: https://stackoverflow.com/questions/111102/how-does-a-javascript-closure-work
  [6]: http://ejohn.org/blog/partial-functions-in-javascript/

JavaScript curry: what are the practical applications?

&gt; **Possible Duplicate:**  
&gt; [JavaScript: var functionName = function() {} vs function functionName() {}](https://stackoverflow.com/questions/336859/javascript-var-functionname-function-vs-function-functionname)  

&lt;!-- End of automatically inserted text --&gt;

What&#39;s the difference between:

    function sum(x, y) {
      return x+y;
    }

    // and 
  
    var sum = function (x, y) {
        return x+y;
    }

Why is one used over the other?



The difference between the two functions? (&quot;function x&quot; vs &quot;var x = function&quot;)

I&#39;m trying to find a way to &quot;pretty print&quot; a JavaScript data structure in a human-readable form for debugging. 

I have a rather big and complicated data structure being stored in JS and I need to write some code to manipulate it. In order to work out what I&#39;m doing and where I&#39;m going wrong, what I really need is to be able to see the data structure in its entirety, and update it whenever I make changes through the UI.

All of this stuff I can handle myself, apart from finding a nice way to dump a JavaScript data structure to a human-readable string. JSON would do, but it really needs to be nicely formatted and indented. I&#39;d usually use Firebug&#39;s excellent DOM dumping stuff for this, but I really need to be able to see the entire structure at once, which doesn&#39;t seem to be possible in Firebug.

JavaScript data formatting/pretty printer

I&#39;ve seen a fair share of ungainly XML-&gt;JSON code on the web, and having interacted with Stack&#39;s users for a bit, I&#39;m convinced that this crowd can help more than the first few pages of Google results can.

So, we&#39;re parsing a weather feed, and we need to populate weather widgets on a multitude of web sites.  We&#39;re looking now into Python-based solutions.

This public [weather.com RSS feed][1] is a good example of what we&#39;d be parsing (*our actual weather.com feed contains additional information because of a partnership w/them*).

In a nutshell, how should we convert XML to JSON using Python?

  [1]: http://rss.weather.com/weather/rss/local/14607?cm_ven=LWO&amp;cm_cat=rss&amp;par=LWO_rss

Converting XML to JSON using Python?

I need to [serialize](https://en.wikipedia.org/wiki/Serialization) an object to [JSON](https://www.json.org/). I&#39;m using [jQuery](https://api.jquery.com/). Is there a &quot;standard&quot; way to do this?

My specific situation: I have an array defined as shown below:

    var countries = new Array();
    countries[0] = &#39;ga&#39;;
    countries[1] = &#39;cd&#39;;
    ...

and I need to turn this into a string to pass to [`$.ajax()`](https://www.w3schools.com/jquery/ajax_ajax.asp) like this:

    $.ajax({
        type: &quot;POST&quot;,
        url: &quot;Concessions.aspx/GetConcessions&quot;,
        data: &quot;{&#39;countries&#39;:[&#39;ga&#39;,&#39;cd&#39;]}&quot;,
    ...



Serializing to JSON in jQuery

When manually generating a JSON object or array, it&#39;s often easier to leave a trailing comma on the last item in the object or array.  For example, code to output from an array of strings might look like (in a C++ like pseudocode):

    s.append(&quot;[&quot;);
    for (i = 0; i &lt; 5; ++i) {
        s.appendF(&quot;\&quot;%d\&quot;,&quot;, i);
    }
    s.append(&quot;]&quot;);
    
giving you a string like

    [0,1,2,3,4,5,]

Is this allowed?

Can you use a trailing comma in a JSON object?

I&#39;m taking my first crack at [Ajax][1] with jQuery. I&#39;m getting my data onto my page, but I&#39;m having some trouble with the JSON data that is returned for Date data types. Basically, I&#39;m getting a string back that looks like this:

    /Date(1224043200000)/

From someone totally new to JSON - How do I format this to a short date format? Should this be handled somewhere in the jQuery code? I&#39;ve tried the `jQuery.UI.datepicker` plugin using `$.datepicker.formatDate()` without any success.

FYI: Here&#39;s the solution I came up with using a combination of the answers here:

    function getMismatch(id) {
      $.getJSON(&quot;Main.aspx?Callback=GetMismatch&quot;,
        { MismatchId: id },

        function (result) {
          $(&quot;#AuthMerchId&quot;).text(result.AuthorizationMerchantId);
          $(&quot;#SttlMerchId&quot;).text(result.SettlementMerchantId);
          $(&quot;#CreateDate&quot;).text(formatJSONDate(Date(result.AppendDts)));
          $(&quot;#ExpireDate&quot;).text(formatJSONDate(Date(result.ExpiresDts)));
          $(&quot;#LastUpdate&quot;).text(formatJSONDate(Date(result.LastUpdateDts)));
          $(&quot;#LastUpdatedBy&quot;).text(result.LastUpdateNt);
          $(&quot;#ProcessIn&quot;).text(result.ProcessIn);
        }
      );

      return false;
    }

    function formatJSONDate(jsonDate) {
      var newDate = dateFormat(jsonDate, &quot;mm/dd/yyyy&quot;);
      return newDate;
    }

This solution got my object from the callback method and displayed the dates on the page properly using the date format library.

  [1]: http://en.wikipedia.org/wiki/Ajax_%28programming%29


How do I format a Microsoft JSON date?

Is it possible to catch an error when using JSONP with jQuery? I&#39;ve tried both the $.getJSON and $.ajax methods but neither will catch the 404 error I&#39;m testing. Here is what I&#39;ve tried (keep in mind that these all work successfully, but I want to handle the case when it fails):

    jQuery.ajax({
        type: &quot;GET&quot;,
        url: handlerURL,
        dataType: &quot;jsonp&quot;,
        success: function(results){
            alert(&quot;Success!&quot;);
        },
        error: function(XMLHttpRequest, textStatus, errorThrown){
            alert(&quot;Error&quot;);
        }
    });

And also:

    jQuery.getJSON(handlerURL + &quot;&amp;callback=?&quot;, 
        function(jsonResult){
            alert(&quot;Success!&quot;);
        });

I&#39;ve also tried adding the $.ajaxError but that didn&#39;t work either:

    jQuery(document).ajaxError(function(event, request, settings){
       alert(&quot;Error&quot;);
    });

Thanks in advance for any replies!

How do I catch jQuery $.getJSON (or $.ajax with datatype set to &#39;jsonp&#39;) error when using JSONP?

Are there any security issues that should be considered when using JSONP?



Is JSONP safe to use?

I am looking to return some JSON across domains and I understand that the way to do this is through JSONP rather than pure JSON. &lt;br /&gt;
I am using ASP.net MVC so I was thinking about just extending the `JsonResult` type and then extending the Controller so that it also implemented a Jsonp method. &lt;br/&gt;
Is this the best way to go about it or is there a built-in `ActionResult` that might be better?

&lt;hr /&gt;

**Solution**:  I went ahead and did that.  Just for reference sake I added a new result:

````
public class JsonpResult : System.Web.Mvc.JsonResult
{
    public override void ExecuteResult(ControllerContext context)
    {
        if (context == null)
        {
            throw new ArgumentNullException(&quot;context&quot;);
        }

        HttpResponseBase response = context.HttpContext.Response;

        if (!String.IsNullOrEmpty(ContentType))
        {
            response.ContentType = ContentType;
        }
        else
        {
            response.ContentType = &quot;application/javascript&quot;;
        }
        if (ContentEncoding != null)
        {
            response.ContentEncoding = ContentEncoding;
        }
        if (Data != null)
        {
            // The JavaScriptSerializer type was marked as obsolete prior to .NET Framework 3.5 SP1
        #pragma warning disable 0618
            HttpRequestBase request = context.HttpContext.Request;

            JavaScriptSerializer serializer = new JavaScriptSerializer();
            response.Write(request.Params[&quot;jsoncallback&quot;] + &quot;(&quot; + serializer.Serialize(Data) + &quot;)&quot;);
        #pragma warning restore 0618
        }
    }
}
````

and also a couple of methods to a superclass of all my controllers:

 
````
protected internal JsonpResult Jsonp(object data)
{
    return Jsonp(data, null /* contentType */);
}

protected internal JsonpResult Jsonp(object data, string contentType)
{
    return Jsonp(data, contentType, null);
}

protected internal virtual JsonpResult Jsonp(object data, string contentType, Encoding contentEncoding)
{
    return new JsonpResult
    {
        Data = data,
        ContentType = contentType,
        ContentEncoding = contentEncoding
    };
}

````

Works like a charm.  

ASP.net MVC returning JSONP

To add some basic error handling, I wanted to rewrite a piece of code that used jQuery&#39;s $.getJSON to pull in some photo&#39;s from Flickr. The reason for doing this is that $.getJSON doesn&#39;t provide error handling or work with timeouts.

Since $.getJSON is just a wrapper around $.ajax I decided to rewrite the thing and surprise surprise, it works flawlessly.

Now the fun starts though. When I deliberately cause a 404 (by changing the URL) or cause the network to timeout (by not being hooked up to the interwebs), the error event doesn&#39;t fire, at all. I&#39;m at a loss as to what I&#39;m doing wrong. Help is much appreciated.

Here&#39;s the code:

    $(document).ready(function(){
    
        // var jsonFeed = &quot;http://api.flickr.com/services/feeds/photos_public.gne&quot;; // correct URL
        var jsonFeed = &quot;http://api.flickr.com/services/feeds/photos_public.gne_______&quot;; // this should throw a 404
    
        $.ajax({
            url: jsonFeed,
            data: { &quot;lang&quot; : &quot;en-us&quot;,
                    &quot;format&quot; : &quot;json&quot;,
                    &quot;tags&quot; : &quot;sunset&quot;
            },
            dataType: &quot;jsonp&quot;,
            jsonp: &quot;jsoncallback&quot;,
            timeout: 5000,
            success: function(data, status){
                $.each(data.items, function(i,item){
                    $(&quot;&lt;img&gt;&quot;).attr(&quot;src&quot;, (item.media.m).replace(&quot;_m.&quot;,&quot;_s.&quot;))
                              .attr(&quot;alt&quot;, item.title)
                              .appendTo(&quot;ul#flickr&quot;)
                              .wrap(&quot;&lt;li&gt;&lt;a href=\&quot;&quot; + item.link + &quot;\&quot;&gt;&lt;/a&gt;&lt;/li&gt;&quot;);
                    if (i == 9) return false;
                });
            },
            error: function(XHR, textStatus, errorThrown){
                alert(&quot;ERREUR: &quot; + textStatus);
                alert(&quot;ERREUR: &quot; + errorThrown);
            }
        });

    });


I&#39;d like to add that this question was asked when jQuery was at version 1.4.2

jQuery ajax (jsonp) ignores a timeout and doesn&#39;t fire the error event

How can you handle errors in a getJSON call? Im trying to reference a cross-domain script service using jsonp, how do you register an error method? 

Content Type	Original Author	Original Content on Stackoverflow
Question	Zach	View Question on Stackoverflow
Solution 1 - Javascript	John Millikin	View Answer on Stackoverflow
Solution 2 - Javascript	Florian Bösch	View Answer on Stackoverflow

Best content type to serve JSONP?

Javascript Problem Overview

Javascript Solutions

Solution 1 - Javascript

Solution 2 - Javascript

Smart pointers: who owns the object?

Why shouldn't I use "Hungarian Notation"?

Attributions