JSONP works by constructing a “script” element (either in HTML markup or inserted into the DOM via JavaScript), which requests to a remote data service location. The response is a javascript loaded on to your browser with name of the pre-defined function along with parameter being passed that is tht JSON data being requested. When the script executes, the function is called along with JSON data, allowing the requesting page to receive and process the data.
For Further Reading Visit: http://scn.sap.com/community/developer-center/front-end/blog/2013/07/15/secret-behind-jsonphttps://blogs.sap.com/2013/07/15/secret-behind-jsonp/
client side snippet of code
<!DOCTYPE html>
<html lang="en">
<head>
<title>AvLabz - CORS : The Secrets Behind JSONP </title>
<meta charset="UTF-8" />
</head>
<body>
<input type="text" id="username" placeholder="Enter Your Name"/>
<button type="submit" onclick="sendRequest()"> Send Request to Server </button>
<script>
"use strict";
//Construct the script tag at Runtime
function requestServerCall(url) {
var head = document.head;
var script = document.createElement("script");
script.setAttribute("src", url);
head.appendChild(script);
head.removeChild(script);
}
//Predefined callback function
function jsonpCallback(data) {
alert(data.message); // Response data from the server
}
//Reference to the input field
var username = document.getElementById("username");
//Send Request to Server
function sendRequest() {
// Edit with your Web Service URL
requestServerCall("http://localhost/PHP_Series/CORS/myService.php?callback=jsonpCallback&message="+username.value+"");
}
</script>
</body>
</html>
Server side piece of PHP code
<?php
header("Content-Type: application/javascript");
$callback = $_GET["callback"];
$message = $_GET["message"]." you got a response from server yipeee!!!";
$jsonResponse = "{\"message\":\"" . $message . "\"}";
echo $callback . "(" . $jsonResponse . ")";
?>
