function GetQueryStringParams(sParam)
{
    var sPageURL = window.location.search.substring(1);
    var sURLVariables = sPageURL.split('&');
    for (var i = 0; i < sURLVariables.length; i++)
    {
        var sParameterName = sURLVariables[i].split('=');
        if (sParameterName[0] == sParam)
        {
            return decodeURIComponent(sParameterName[1])
        }
    }
}

$(document).ready(function()
    {
        $('#submit').click(function() {
            var username = $('#username').val();
            var password = $('#password').val();
            user_query = $.post(
                "https://www..../check_password",
                {'username': username, 'password': password, 'account_linking_token': GetQueryStringParams('account_linking_token')},
                function(data) {
                    var authorization_code = '';
                    if (data != '0') {
                        authorization_code = '&authorization_code=userid' + data;
                    }
                    window.location.href = GetQueryStringParams('redirect_uri') + authorization_code;
                },
                'text'
            );
        });
    }
);