How to call nodeJs helper.js from angular controller

I have an angular controller $http.get("/videos?sessionId="+helpers.isAuthenticated.then(function(res){ console.log(res); });

this function is unathorized right now because in api routes is necesary to call a function isAuthenticated

app.get('/videos', helpers.isAuthenticated,videos.get);

but when I try I got an error

ReferenceError: helpers is not defined

Thanks in advance

via Juan Carlos Pacheco Hernandez