跨域解决方案

使用cors库

npm i cors  // 安装

app.use(require('cors')()) // 使用

如下

app.all('*', function(req, res, next) {
  //设为指定的域
  res.header('Access-Control-Allow-Origin', "*");
  res.header("Access-Control-Allow-Headers", "X-Requested-With");
  res.header('Access-Control-Allow-Headers', 'Content-Type');
  res.header("Access-Control-Allow-Methods", "PUT,POST,GET,DELETE,OPTIONS");
  res.header('Access-Control-Allow-Credentials', true);
  res.header("X-Powered-By", ' 3.2.1');
  next();
});

如下

app.use((req,res,next)=>{
    res.header('Access-Control-Allow-Origin', "*");
    res.header('Access-Control-Allow-Headers', 'Content-Type');
    res.header("Access-Control-Allow-Methods", "PUT,POST,GET,DELETE,OPTIONS");
    next();
})