jsonp原理

借助script标签发送跨域请求，只支持get方法

客户端：client.html

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>JSONP 客户端</title>
</head>
<body>
  <script>
    function jsonp (url, params, callback) {
      var funcName = 'jsonp_' + Date.now() + Math.random().toString().substr(2, 5)

      if (typeof params === 'object') {
        var tempArr = []
        for (var key in params) {
          var value = params[key]
          tempArr.push(key + '=' + value)
        }
        params = tempArr.join('&')
      }

      var script = document.createElement('script')
      script.src = url + '?' + params + '&callback=' + funcName
      document.body.appendChild(script)

      window[funcName] = function (data) {
        callback(data)

        delete window[funcName]
        document.body.removeChild(script)
      }
    }
    jsonp('http://localhost/jsonp/server.php', { id: 1 }, function (res) {
      console.log(res)
    })

    jsonp('http://localhost/jsonp/server.php', { id: 1 }, function (res) {
      console.log(res)
    })
  </script>
</body>
</html>

服务器：server.php

<?php
$data = array(
    'id' => 1,
    'name' => 'zs'
);
if (empty($_GET['callback'])) {
  header('Content-Type: application/json');
  echo json_encode($data);
  exit();
}
// 如果客户端采用的是 script 标记对我发送的请求
// 一定要返回一段 JavaScript
header('Content-Type: application/javascript');
$result = json_encode($data);
$callback_name = $_GET['callback'];
echo "typeof {$callback_name} === 'function' && {$callback_name}({$result})";

jsonp原理

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