function loginUser() {

    var version = "";
    var sessionId = "Hello!";

    .
    .   //some code here
    .

    jQuery.jsonRPC.request('getVersion', {
        params : {},
        success : function(result) {
            version = result.result[1];
            jQuery.ajax({
                url:"index.php?module=SDK&action=SDKAjax&file=marte/src/1100/GetLoginInformationAjax",
                dataType:"json",
                type: "post",
                data: "function=get_loginInfo",
                async: false,
                cache: false,
                success: function(res){
                    user = res['user'];
                    password = res['password'];
                    try {
                        jQuery.jsonRPC.request('login', {
                            params : [ version, user, password ],
                            success : function(result) {
                                sessionId = JSON.parse(JSON.stringify(result)).result.sessionId;
                                alert("Test 1 "+sessionId);
                            },
                            error : function(result) {
                                alert(JSON.stringify(result));
                            }
                        });
                    } catch (e) {
                        console.log(JSON.stringify(e));
                    }
                },
                error: function(){
                    alert('Login error');
                }
            });
        },
        error : function(result) {
            console.log(JSON.stringify(result));
        }
    });

    alert(sessionId+" Test 2");
    return sessionId;
}