How to wait till jsonrpc client returns response.

[gubkamatus]

I have JS client:
In JS I have function:
----------------------Start code-------------------
var codebook_onlinedb;

function getCodeBook() {
jsonrpcclient = new jsonrpcphp('http://some.url/server.php', function() {
jsonrpcclient.cCodeBook.getCodeBook("inout", function(jsonRpcObj) {
codebook_onlinedb = $.map(jsonRpcObj.result, function(value, index) {
return [value];
});
});
});

function doSomething() {
console.log( 'main: ' + codebook_onlinedb);
}

var x = getCodeBook();
doSomething();

End of code

In firebug console: http://oi61.tinypic.com/2u7m1r9.jpg
In firebug console I have two POST calls. First gives me a list of methods and second gives me correct response to my task but my JS function doSomething is performed in first POST. Why? Or how can I wait to correct response from second POST. Thanks.