JSONP is a method to transfer JSON data without considering cross-domain issues.
JSONP does not use XMLHttpRequest objects.
JSONP uses the <script> tag instead.
Introduction to JSONP
JSONP refers to JSON with Padding.
Requesting files from another domain can cause problems due to cross-domain policies.
Requesting external scripts from another domain does not have this problem.
JSONP takes advantage of this and uses script tags instead of XMLHttpRequest objects.
<script src="demo_jsonp.php">
JSONP application
Server-side JSONP format data
If the customer wants to visit: https://www.runoob.com/try/ajax/jsonp.php?jsoncallback=callbackFunction.
Assume that the customer expects to return data: ["customername1", "customername2"].
The data actually returned to the client is displayed as: callbackFunction (["customername1", "customername2"]).
The server file jsonp.php code is:
<?php
header('Content-type: application/json');
//获取回调函数名
$jsoncallback = htmlspecialchars($_REQUEST ['jsoncallback']);
//json数据
$json_data = '["customername1","customername2"]';
//输出jsonp格式的数据
echo $jsoncallback . "(" . $json_data . ")";
?>
Client:
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>JSONP 实例</title>
</head>
<body>
<div id="divCustomers"></div>
<script type="text/javascript">
function callbackFunction(result, methodName)
{
var html = '<ul>';
for(var i = 0; i < result.length; i++)
{
html += '<li>' + result[i] + '</li>';
}
html += '</ul>';
document.getElementById('divCustomers').innerHTML = html;
}
</script>
<script type="text/javascript" src="https://www.xxxx.com/try/ajax/jsonp.php?jsoncallback=callbackFunction"></script>
</body>
</html>
jQuery uses JSONP:
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>JSONP 实例</title>
<script src="https://cdn.static.runoob.com/libs/jquery/1.8.3/jquery.js"></script>
</head>
<body>
<div id="divCustomers"></div>
<script>
$.getJSON("https://www.runoob.com/try/ajax/jsonp.php?jsoncallback=?", function(data) {
var html = '<ul>';
for(var i = 0; i < data.length; i++)
{
html += '<li>' + data[i] + '</li>';
}
html += '</ul>';
$('#divCustomers').html(html);
});
</script>
</body>
</html>
