node接口请求数据，发生跨域错误

//设置允许跨域访问该服务.
app.all(‘*‘, function (req, res, next) {
  res.header(‘Access-Control-Allow-Origin‘, ‘*‘);
  //Access-Control-Allow-Headers ,可根据浏览器的F12查看,把对应的粘贴在这里就行
  res.header(‘Access-Control-Allow-Headers‘, ‘Content-Type‘);
  res.header(‘Access-Control-Allow-Methods‘, ‘*‘);
  res.header(‘Content-Type‘, ‘application/json;charset=utf-8‘);
  next();
});
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原文链接：https://blog.csdn.net/qq_34545192/article/details/80177362

router.all(‘*‘, function (req, res, next) {

  res.header(‘Access-Control-Allow-Origin‘, ‘*‘);
  //Access-Control-Allow-Headers ,
  res.header(‘Access-Control-Allow-Headers‘, ‘Content-Type‘);
  res.header(‘Access-Control-Allow-Methods‘, ‘*‘);
  res.header(‘Content-Type‘, ‘application/json;charset=utf-8‘);
  next();
});