JSONP callback function enables cross-domain communication by allowing a

After delving into the world of JSONP callback functions, I decided to familiarize myself with the concept by researching articles.

To further understand JSONP, I uploaded a JSON file onto the server - json file

Below is the JavaScript code I used to fetch the data. The request is made from localhost to abhishekprakash.com.

var xhr;
var dataList;
xhr = new XMLHttpRequest();

xhr.open('GET', 'http://abhishekprakash.com/script/example.json?callback=func_callbk',  true);
xhr.send();

func_callback = function(data){
    alert(data.data.people[0].id);
}

xhr.onreadystatechange = function(){
if(xhr.readyState == 4){
            console.log(dataList);
    }
};

Upon checking the console, this is the response I received:

While the callback function is triggered, it does not include the JSON data. What could be the missing piece here?

Your assistance is greatly appreciated.

Thank you

Answer ā„–1

The service in that example is designed to return JSON data, not JSONP.

JSONP's purpose is to overcome security restrictions imposed by the Same Origin Policy, which prevents JavaScript from one domain (A) from making GET requests to resources on another domain (B), thus restricting cross-domain data retrieval.

To address this issue, JSONP requires cooperation from domain B for cross-domain data sharing. In JSONP, the script on domain A specifies a callback function name and includes the URL of domain B in the document, treating it as a regular external JavaScript file. Domain B then outputs the data in the following format:

callbackFuncName({ data : foo, ... });

This means that domain B generates a Javascript snippet that calls the specified callback function with the data.

Without explicit cooperation from domain B, obtaining a JSONP response from it is not possible.

Answer ā„–2

Working with XHR has its limitations due to cross-domain rules; to utilize JSONP, you must incorporate a script element:

function designated_function()
{
    console.log(arguments);
}

var script_element = document.createElement('script');
script_element.type = 'text/javascript';
script_element.src = 'http://example.com/script/data.json?callback=designated_function';
var script_location = document.getElementsByTagName('script')[0];
script_location.parentNode.insertBefore(script_element, script_location);

It is important to ensure that your server sends the correct response, as demonstrated by Ian in the comments:

designated_function('hello world')

Update

If you prefer to avoid using JSONP (such as when the response must always be JSON), explore CORS for a solution as detailed in this referenced answer.

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