As Ajax stands, I believe it is made available to make asynchronous call to server but why does it also allow to be set to synchronous as an option?
What would be the case when you want synchronous operation using Ajax?
AJAX predates many of the libraries, extensions, and languages we currently use for handling asynchronous interactions between client and server. Initially, deferred handling of a response was not easily accomplished on the client, so the design of AJAX allowed for the developer to indicate that some operations should wait for response by executing synchronously.
The ability to operate synchronously is still included in AJAX to maintain legacy code. It is really difficult to come up with a use case today that would require the use of a synchronous AJAX call.
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As I found, it is possible to manipulate and change Ajax code in browser console by client. For example, Ajax wants to call a method and pass id to controller. As I mentioned above, how we can secure our code from interference by client?
Thank you all
Security must always be implemented on the server side, because anything you do on the client side can be ignored, overstep, modified, etc very easily. In fact, anyone can use software like Postman to make a completely custom HTML request to any server.
Don't ever rely on any client-side software in terms of security for your server. If you want keep your server safe, then make a safe server.
I'm debugging some tricky Ajax code without a server side, in fact I have no domain etc to even put any server-side code on.
I would like to find some very minimal Ajax JSON(P) testing or debugging webservice or web API that just sends something back. Something like a ping or noop or ack.
I would prefer something small, fast, and reliable, preferably provided by major Internet companies such as Google, Microsoft, or Yahoo.
Ideally it would support these features, though none are totally essential:
Support JSONP.
Parametrically return success or various kinds of failure.
Parametrically delay a specified time before responding.
Parametrically support or reject CORS requests.
Parametric control over HTTP headers.
Parametrically describe the object returned.
In fact the most basic form of such a service from a major provider would also be useful for determining that Internet access is available, at least to a degree beyond navigator.onLine.
jsFiddle actually supports some of the features I'm looking for with their “Echo Javascript file and XHR requests”.
To improve user experience “echo” features has been created. This allows to test XHR requests, add javascript files, create workers - all from one fiddle, so it is more transparent for the user reading the code. XHR requests are split to HTML, JSON, JSONP and XML. Gist and github responses are similar to the echo feature and go nicely in pair with storing fiddles in gist and github.
They're not really intended for use outside jsFiddle though. Some limitations:
HTTP POST must be used for everything except JSONP and JavaScript.
CORS is not supported.
Of the desired features I listed, it supports at least:
specifying a delay
describing an object to return
What are the benefits of a XML HTTP request? A given server could send data (e.g. some JSON serialization) for a normal request (non-XHR) as it would send data for a XHR request. And that data could be processed asynchronously (by a browser for example) as well. So why was the XMLHttpRequest invented?
Some things I can think of:
To use the same URL for HTML and a web service
To let the server know that this must be processed fast.
As far as I recall, one of the first uses of XmlHttpRequest was for OWA, which used WebDAV on the wire. So show me how to do methods other than GET/POST without it.
One important thing about XHR is that it's asynchronous and you can have several concurrently running XHR requests. For example you can have several informers on your web page, all updating independently and concurrently.
XMLHttpRequest (or ActiveXObject in IE) is what allows Javascript to make HTTP requests. It was created to be able to retrieve data in Javascript without having to change the page/refresh the browser.
There are non-javascript ways of retrieving data without refreshing the page, but if you are using Javascript XMLHttpRequest is the way to go. Many libraries have simplified the use of this call by implementing ajax functions in their libraries (jQuery.ajax() for example) which causes most people to not even realize that XMLHttpRequest is the underlying call behind it.
I think the biggest reason it exists is that it predates an Ajax JSON request. It was originally the only way to do AJAX based things. It's still useful when requesting an HTML page and populating an HTML element with the information requested. It's much simpler to use XHR in that instance instead of parsing the JSON and reading out a variable.
I guess the simple answer is that if you're looking for a single piece of data it would be a simpler request to process.
what is different between ajax and webservices. Anybody provide with some examples?
It's nonsensical to compare these things.
"Ajax" is a process that occurs in the browser. It is the act of calling some local server-side page, without refreshing the "main" viewing area, and then doing various things with that result (grabbing the data, making changes, changing the existing DOM (adding elements), whatever).
Webservices are a Serverside-thing that allows you to call methods, in your code, but have that call actually go to a remote machine. The call to the Webservice is generally also made server-side.
The term "Ajax" is generally used :
When the request is sent by a browser (client-side) to a server
When the transfered data is XML or JSON or HTML.
The word "webservice" is generally used :
When the request is sent by a server to another server, without a browser being involved
When the transfered data is SOAP -- at least when it's a SOAP webservice ^^ (Opposed to REST, for instance, which generally doesn't imply SOAP)
But I'd say that Ajax is basically some specific kind of webservice.
i think ajax and web services are kind of similar, here is why i think so.
as i understood it, in your app sometimes you will have to implement an "API" which has several useful functions. and it is those functions which are called "web services". these 'functions' acts in response to the http requests and "does" something with the data provided.
in ajax siimilar kind of work happens as well,just through javascript thats it.
so, to sum it all up, an API has 'web services' within it, and ajax behaves like 'web services'. in this manner, yes i think it is correct to call ajax and web services similar.
Is there any difference in performance ( speed wise ) between a synchronous request and and asynchronous request?
What all are the reasons for using an asynchronous request??
You should mostly always use an asynchronous Ajax Request, in fact I know only about one place where a synchronous Ajax Request should be used which is if you're in an Ajax Request embedding a new JavaScript file on the client and then referencing types and/or objects from that JavaScript file in the return from the original Ajax Request. Then the fetching of this new JS file should (or can sanely) be included through using a synchronous Ajax Request...
Other then that you should always use asynchronous Ajax Requests. The most important reason is that a synchronous Ajax Request makes the UI (browser) unresponsive...
#Thomas Hansen answer is right but I found a clear explanation with benefits of Asynchronous.
Synchronous is simple, but wait for the server response, thus block the execution of the caller for a period and slower than asynchronous while processing the request.
Asynchronous is required setting, do not wait after submitting the request and immediately return control to the caller, thus faster than Synchronous.
I am coming here when I have to use upload control which has both functionalities in the question and looking the pros and cons of this functionality.
I got the another link which explained with a real example. (the link is the specific tool, so understand the logic)
The major difference is the response time from our servers. At the time of upload, synchronous will validate file and create the passcode in real-time. Asynchronous will send the file to our server's queue and deliver notification via email once it is processed.
Synchronous is not ideal for multiple, large CSV file since you will need to wait until the file is processed by the server to submit another request. On large files, this also may cause your browsers to return with timeout errors due to the server being too busy. If you have multiple files, asynchronous will allow you to submit multiple files to the server queue to be processed with a email receipt once completed.
https://www.aspsnippets.com/Articles/Difference-between-Synchronous-Sync-and-Asynchronous-Async-Request-Call-in-AJAX.aspx
there can be serious performance implications caused when it come to highly database intensive applications .. although it's very unlikely to happen .. and sending many Synchronous ajax calls can create a backlog .. so if the application database intensive and sending so many request at once it is better to make it asynchronous.
when its set to asynch the browser will fail all unresponsive request and continue with new once..