Node express 官方示例cors跨域解析

var express = require('../..');
var logger = require('morgan');
var app = express();
var bodyParser = require('body-parser');
var api = express();

// app middleware

app.use(express.static(__dirname + '/public'));

// api middleware

api.use(logger('dev'));
api.use(bodyParser.json());

/**
 * CORS support.
 */

api.all('*', function(req, res, next){
  if (!req.get('Origin')) return next();
  // use "*" here to accept any origin
  res.set('Access-Control-Allow-Origin', 'http://localhost:3000');
  res.set('Access-Control-Allow-Methods', 'PUT');
  res.set('Access-Control-Allow-Headers', 'X-Requested-With, Content-Type');
  // res.set('Access-Control-Allow-Max-Age', 3600);
  if ('OPTIONS' == req.method) return res.send(200);
  next();
});

/**
 * PUT an existing user.
 */
api.put('/user/:id', function(req, res){
  console.log('req.body'+req.body);
   console.log(req.body);
  res.send(204);
});
app.listen(3000);
api.listen(3001);
console.log('app listening on 3000');
console.log('api listening on 3001');

var req = new XMLHttpRequest;
  req.open('PUT', 'http://localhost:3001/user/1', false);
  req.setRequestHeader('Content-Type', 'application/json');
  req.send('{"name":"tobi","species":"ferret"}');
  console.log(req.responseText);