What are the differences between JSON and JSONP

Question

Format wise  file type wise and practical use wise

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JSONP is essentially  JSON with extra code  like a function call wrapped around the data  It allows the data to be acted on during parsing

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JSON JSON  JavaScript Object Notation  is a convenient way to transport data between applications  especially when the destination is a JavaScript application  Example  Here is a minimal example that uses JSON as the transport for the server response  The client makes an Ajax request with the jQuery shorthand function   getJSON  The server generates a hash  formats it as JSON and returns this to the client  The client formats this and puts it in a page element  Server  get   json  do  content type  json  content      response    gt   Sent via JSON                timestamp   gt  Time now               random      gt  rand 10000     content to json end  Client  var url   host prefix     json     getJSON url  function json        quot  json-response quot   html JSON stringify json  null  2         Output          quot response quot    quot Sent via JSON quot       quot timestamp quot    quot 2014-06-18 09 49 01  0000 quot       quot random quot   6074      JSONP  JSON with Padding  JSONP is a simple way to overcome browser restrictions when sending JSON responses from different domains from the client  The only change on the client side with JSONP is to add a callback parameter to the URL Server  get   jsonp  do  callback   params  callback    content type  js  content      response    gt   Sent via JSONP                timestamp   gt  Time now               random      gt  rand 10000      quot   callback    content to json   quot  end  Client  var url   host prefix     jsonp callback       getJSON url  function jsonp        quot  jsonp-response quot   html JSON stringify jsonp  null  2         Output        quot response quot    quot Sent via JSONP quot      quot timestamp quot    quot 2014-06-18 09 50 15  0000 quot      quot random quot   364

User · Answer

JSONP is a simple way to overcome browser restrictions when sending JSON responses from different domains from the client   But the practical implementation of the approach involves subtle differences that are often not explained clearly   Here is a simple tutorial that shows JSON and JSONP side by side   All the code is freely available at Github and a live version can be found at http   json-jsonp-tutorial craic com

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JSONP stands for    JSON with Padding    and it is a workaround for loading data from different domains  It loads the script into the head of the DOM and thus you can access the information as if it were loaded on your own domain  thus by-passing the cross domain issue   jsonCallback         sites                                siteName    JQUERY4U                domainName    http   www jquery4u com                description     1 jQuery Blog for your Daily News  Plugins  Tuts Tips  amp amp  Code Snippets                                     siteName    BLOGOOLA                domainName    http   www blogoola com                description    Expose your blog to millions and increase your audience                                     siteName    PHPSCRIPTS4U                domainName    http   www phpscripts4u com                description    The Blog of Enthusiastic PHP Scripters                        function      var url    http   www jquery4u com scripts jquery4u-sites json callback        ajax      type   GET       url  url      async  false      jsonpCallback   jsonCallback       contentType   application json       dataType   jsonp       success  function json           console dir json sites              error  function e           console log e message                 jQuery     Now we can request the JSON via AJAX using JSONP and the callback function we created around the JSON content  The output should be the JSON as an object which we can then use the data for whatever we want without restrictions

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Basically  you re not allowed to request JSON data from another domain via AJAX due to same-origin policy  AJAX allows you to fetch data after a page has already loaded  and then execute some code call a function once it returns  We can t use AJAX but we are allowed to inject  lt script gt  tags into our own page and those are allowed to reference scripts hosted at other domains    Usually you would use this to include libraries from  a CDN such as jQuery  However  we can abuse this and use it to fetch data instead  JSON is already valid JavaScript  for the most part   but we can t just return JSON in our script file  because we have no way of knowing when the script data has finished loading and we have no way of accessing it unless it s assigned to a variable or passed to a function  So what we do instead is tell the web service to call a function on our behalf when it s ready   For example  we might request some data from a stock exchange API  and along with our usual API parameters  we give it a callback  like  callback callThisWhenReady  The web service then wraps the data with our function and returns it like this  callThisWhenReady     data       Now as soon as the script loads  your browser will try to execute it  as normal   which in turns calls our arbitrary function and feeds us the data we wanted   It works much like a normal AJAX request except instead of calling an anonymous function  we have to use named functions   jQuery actually supports this seamlessly for you by creating a uniquely named function for you and passing that off  which will then in turn run the code you wanted

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JSONP is JSON with padding  That is  you put a string at the beginning and a pair of parentheses around it  For example     JSON   name   stackoverflow   id  5    JSONP func   name   stackoverflow   id  5      The result is that you can load the JSON as a script file  If you previously set up a function called func  then that function will be called with one argument  which is the JSON data  when the script file is done loading  This is usually used to allow for cross-site AJAX with JSON data  If you know that example com is serving JSON files that look like the JSONP example given above  then you can use code like this to retrieve it  even if you are not on the example com domain   function func json     alert json name     var elm   document createElement  script    elm setAttribute  type    text javascript    elm src    http   example com jsonp   document body appendChild elm

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JSONP allows you to specify a callback function that is passed your JSON object   This allows you to bypass the same origin policy and load JSON from an external server into the JavaScript on your webpage

User · Answer

JSONP is JSON with extra code    would be too easy for the real world  No  you gotta have little discrepancies  What   s the fun in programming if everything just works   Turns out JSON is not a subset of JavaScript  If all you do is take a JSON object and wrap it in a function call  one day you will be bitten by strange syntax errors  like I was today

[json] What are the differences between JSON and JSONP?

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