How to get a child select box data when using jsgrid / jqgrid

Question

Using two select boxes, a child select box who's value depends on a parent select box value. So when the parent select box value changes, the system loads the child select box data from the database in real time.

I want to get the child select box data to depend on the parent select box, in this case how can I get the child select box data in javascript?

I am trying to use the code below, but it doesn't work.

$('#child-select-box').jsgrid({
    loadComplete : function() {
        console.log($('#child-select-box').val());
    }
});