How can I not authenticate everytime in StackExchange API calls using JS client?

I am using this code from the StackExchange App Documentation to get the user information from StackOverflow.

// For simplicity, we're using jQuery for some things
//   However, the library has no jQuery dependency
$(function(){
// Initialize library
SE.init({ 
    // Parameters obtained by registering an app, these are specific to the SE
    //   documentation site
    clientId: 1, 
    key: 'U4DMV*8nvpm3EOpvf69Rxw((', 
    // Used for cross domain communication, it will be validated
    channelUrl: 'http://ift.tt/1JgVaaL',
    // Called when all initialization is finished
    complete: function(data) { 
        $('#login-button')
            .removeAttr('disabled')
            .text('Run Example With Version '+data.version); 
    }
});

// Attach click handler to login button
$('#login-button').click(function() {

    // Make the authentication call, note that being in an onclick handler
    //   is important; most browsers will hide windows opened without a
    //   'click blessing'
    SE.authenticate({
        success: function(data) { 
            alert(
                'User Authorized with account id = ' + 
                data.networkUsers[0].account_id + ', got access token = ' + 
                data.accessToken
            ); 
        },
        error: function(data) { 
            alert('An error occurred:\n' + data.errorName + '\n' + data.errorMessage); 
        },
        networkUsers: true
    });
});
});

This code works fine but I noticed that everytime it fires and gives the response access_token changes. How I can I just get user information using the access token. Plus this is returning user's data with all the sites he is part of. How can I limit it to just StackOverflow. I am unable to find proper documentation for this.

Can anyone please point me to the JS methods for making API calls from StackExchange API?