以下代码如何用JavaScript实现
$curl = curl_init($url);
curl_setopt($curl, CURLOPT_CUSTOMREQUEST, $method);
curl_setopt($curl, CURLOPT_HTTPHEADER, array("content-type: application/json"));
curl_setopt($curl, CURLOPT_RETURNTRANSFER, true);
curl_setopt($curl, CURLOPT_POSTFIELDS, $data);
$response = curl_exec($curl);
$err = curl_error($curl);
$http_code = curl_getinfo($curl, CURLINFO_HTTP_CODE);
curl_close($curl);
或者说ajax的跨域put请求如何实现