How to implement an authenticated es 7 decorator with babel for my js service module

Question

I'm using babel with decorator stage:0 support in my flux fluxible js project, and I want to use an authenticated decorator for my service api modules to check for a valid user session.

Googling around, there seems to be several posts that explain different variations but couldn't find one definitive docs or instructionals.

Here's what I tried so far, I know that my parameters for the authenticated function are incorrect, and not sure if I need to implement a class for my module rather than just using the exports object.

The part that I couldn't find the docs for is how to implement the decorator itself - in this case something that takes the req parameter the decorated function will receive and checking it.

// how do I change this method so that it can be implemented as a decorator
function checkAuthenticated(req) {

    if (!req.session || !req.session.username)
    {
        throw new Error('unauthenticated');
    }
}

module.exports = {
    @checkAuthenticated
    read: function(req, resource, params, serviceConfig, callback) {
        //@authenticated decorator should allow me to move this out of this here
        //checkAuthenticated(req);
        if (resource === 'product.search') {
            var keyword = params.text;
            if (!keyword || keyword.length === 0) {
                return callback('empty param', null);
            } else {
                searchProducts(keyword, callback);
            }
        }

    }
};

Answer 1

class Http{
  @checkAuthenticated
  read(req, resource, params, serviceConfig, callback) {
    if (resource === 'product.search') {
      var keyword = params.text;
      if (!keyword || keyword.length === 0) {
        return callback('empty param', null);
      } else {
        this.searchProducts(keyword, callback);
      }
    }
  }

  searchProducts(keyword, callback) {
    callback(null, 'worked');
  }
}

function checkAuthenticated(target, key, descriptor) {
    return {
      ...descriptor,
      value: function(){
        console.log(arguments);
        const req = arguments[0];
        if (!req.session || !req.session.username) {
            throw new Error('unauthenticated');
        }
        return descriptor.value.apply(this, arguments);
      }
    };
}

let h = new Http();

h.read(
  { session: { username: 'user' } },
  'product.search',
  { text: 'my keywords' },
  null,
  function(err, result) {
    if (err) return alert(err);
    return alert(result);
  }
);

See jsbin http://jsbin.com/yebito/edit?js,console,output