nodejs,express设置允许跨域请求

//设置跨域访问
app.all("*", function (req, res, next) {
  //设置允许跨域的域名，*代表允许任意域名跨域
  res.header("Access-Control-Allow-Origin", req.headers.origin || '*');
  // //允许的header类型
  res.header("Access-Control-Allow-Headers", "Content-Type, Authorization, X-Requested-With");
  // //跨域允许的请求方式 
  res.header("Access-Control-Allow-Methods", "PUT,POST,GET,DELETE,OPTIONS");
  // 可以带cookies
  res.header("Access-Control-Allow-Credentials", true);
  if (req.method == 'OPTIONS') {
    res.sendStatus(200);
  } else {
    next();
  }
})