Without login access to drive files by api in javascript (web application)

Question

I'm using javascript with drive + spreadsheet api. Now I am able to get the access token. But I tries a lot with stack answers and google guide for get refresh token request. But I did not found any way that how to access the refresh token by access token. Please help me with some code.

My script is:

var _url = https://accounts.google.com/o/oauth2/auth?scope=https://www.googleapis.com/auth/userinfo.profile https://www.googleapis.com/auth/userinfo.email&client_id={my_client_id}&client_secret={My_secret_key}","redirect_uri=httpmypath to currentrunningfile/oauth&response_type=token

function getAccessDetails() {
        var win         =   window.open(_url, "windowname1", 'width=800, height=600'); 

        var pollTimer   =   window.setInterval(function() { 
            try {
                console.log(win.document.URL);
                if (win.document.URL.indexOf(REDIRECT) != -1) {
                    window.clearInterval(pollTimer);
                    var url =   win.document.URL;
                    console.log('url is :'+url);
                    acToken =   gup(url, 'access_token');
                    tokenType = gup(url, 'token_type');
                    expiresIn = gup(url, 'expires_in');
                    console.log('acToken :' + acToken + 'tokenType :' + tokenType + 'expiresIn :' + expiresIn);
                    win.close();

                    validateToken(acToken);
                }
            } catch(e) {
            }
        }, 500);
    }

What is the next step and how to code it for access the refresh token? Actully I want user to login first time to app with their google login details for their drive files access by my app. The next time when user use my app to access his drive files. He can access files without login.