Access to fetch at 'http://localhost:3000/fetch/fetchGet/456' from origin 'null' has been blocked by CORS policy: No 'Access-Control-Allow-Origin' header is present on the requested resource. If an opaque response serves your needs, set the request's mode to 'no-cors' to fetch the resource with CORS disabled.

express跨域_解决方法

解决方法：

服务端添加允许跨域（以下为node.js express框架）

// 允许跨域
app.all('*', function(req, res, next) {
    res.setHeader(
        'Access-Control-Allow-Origin', '*'
    )
    next();
})