Fetch API cannot load
No 'Access-Control-Allow-Origin' header is present on the requested resource. Origin 'http://localhost:5000' is therefore not allowed access. If an opaque response serves your needs, set the request's mode to 'no-cors' to fetch the resource with CORS disabled.
同样的ajax,get可以用,但是post就会出现这种问题
协调后端解决,不同语言设置Access-Control-Allow-Origin的方式不同。