node + express 解决跨域问题

app.all('*', function (req, res, next) { 
          res.header("Access-Control-Allow-Origin", "*");   res.header("Access-Control-Allow-Headers", "X-Requested-With");   res.header("Access-Control-Allow-Methods", "PUT,POST,GET,DELETE,OPTIONS");   res.header("X-Powered-By", ' 3.2.1')   //方便返回json   res.header("Content-Type", "application/json;charset=utf-8");   if (req.method == 'OPTIONS') { 
            //让options请求快速返回     res.sendStatus(200);   } else { 
            next();   } }); 

必须放在应用路由前，建议位置【var app = express()后面。