How to make cross domain request

Question

As you know  the security of the web browser disallows making of cross domain requests  I read a book which says that you should use XMLHTTPRequest only if you can put the files on the server  means put the page you will load to the same requested domain   If you can t - you should search for an alternative   My questions are    What is the cross domain alternative to XMLHTTPRequest  What about WebSockets  Does this technology allow cross domain request    EDIT  It still isn t clear to me     For example  I pull my page from www domain1 com and I need to request javascript from www domain2 com  So the pulled page should include something like    lt script src  www domain2 com script js  gt  lt  script gt    to avoid cross domain restrictions   And I can use JSONP  and request will look like  http   ww domain1 com  callback someFunction js  But  isn t it the same  I just pull js from another domain  Does it avoid cross domain restrictions

User · Answer

You can make cross domain requests using the XMLHttpRequest object. This is done using something called "Cross Origin Resource Sharing". See: http://en.wikipedia.org/wiki/Cross-origin_resource_sharing

Very simply put, when the request is made to the server the server can respond with a Access-Control-Allow-Origin header which will either allow or deny the request. The browser needs to check this header and if it is allowed then it will continue with the request process. If not the browser will cancel the request.

You can find some more information and a working example here: http://www.leggetter.co.uk/2010/03/12/making-cross-domain-javascript-requests-using-xmlhttprequest-or-xdomainrequest.html

JSONP is an alternative solution, but you could argue it's a bit of a hack.

User · Answer

Do a cross-domain AJAX call  Your web-service must support method injection in order to do JSONP   Your code seems fine and it should work if your web services and your web application hosted in the same domain   When you do a   ajax with dataType   jsonp  meaning that jQuery is actually adding a new parameter to the query URL   For instance  if your URL is http   10 211 2 219 8080 SampleWebService sample do then jQuery will add  callback  some random dynamically generated method    This method is more kind of a proxy actually attached in window object  This is nothing specific but does look something like this   window some random dynamically generated method   function actualJsonpData          here actually has reference to the success function mentioned with   ajax       so it just calls the success method like this       successCallback actualJsonData       Check the following for more information  Make cross-domain ajax JSONP request with jQuery

User · Answer

If you re willing to transmit some data and that you don t need to be secured  any public infos  you can use a CORS proxy  it s very easy  you ll not have to change anything in your code or in server side  especially of it s not your server like the Yahoo API or OpenWeather   I ve used it to fetch JSON files with an XMLHttpRequest and it worked fine

[javascript] How to make cross domain request

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