Ajax 跨域访问post 请求，但是在服务器却得到的总是options请求 （req.method==‘OPTIONS’)

原因有俩：

1.跨域

2.此post请求的 content-type不是one of the “application/x-www-form-urlencoded,multipart/form-data, or text/plain”

解决办法：

添加代码

if (req.method === 'OPTIONS') {

console.log('!OPTIONS');

var headers = {};

// IE8 does not allow domains to be specified, just the *

// headers["Access-Control-Allow-Origin"] = req.headers.origin;

headers["Access-Control-Allow-Origin"] = "*";

headers["Access-Control-Allow-Methods"] = "POST, GET, PUT, DELETE, OPTIONS";

headers["Access-Control-Allow-Credentials"] = false;

headers["Access-Control-Max-Age"] = '86400'; // 24 hours

headers["Access-Control-Allow-Headers"] = "X-Requested-With, X-HTTP-Method-Override, Content-Type, Accept";

res.writeHead(200, headers);

res.end();

} else {

//...other requests

}