function dynamicSelect(id1, id2) {
    // Feature test to see if there is enough W3C DOM support
    if (document.getElementById && document.getElementsByTagName) {
        // Obtain references to both select boxes
        var sel1 = document.getElementById(id1);
        var sel2 = document.getElementById(id2);
        // Clone the dynamic select box
        var clone = sel2.cloneNode(true);
        // Obtain references to all cloned options
        var clonedOptions = clone.getElementsByTagName("option");
        // Onload init: call a generic function to display the related options in the dynamic select box
        refreshDynamicSelectOptions(sel1, sel2, clonedOptions);
        // Onchange of the main select box: call a generic function to display the related options in the dynamic select box
        sel1.onchange = function() {
            refreshDynamicSelectOptions(sel1, sel2, clonedOptions);
        };
    }
}
function refreshDynamicSelectOptions(sel1, sel2, clonedOptions) {
    // Delete all options of the dynamic select box
    while (sel2.options.length) {
        sel2.remove(0);
    }
    // Create regular expression objects for "select" and the value of the selected option of the main select box as class names
    var pattern1 = /( |^)(select)( |$)/;
    var pattern2 = new RegExp("( |^)(" + sel1.options[sel1.selectedIndex].value + ")( |$)");
    // Iterate through all cloned options
    for (var i = 0; i < clonedOptions.length; i++) {
        // If the classname of a cloned option either equals "select" or equals the value of the selected option of the main select box
        if (clonedOptions[i].className.match(pattern1) || clonedOptions[i].className.match(pattern2)) {
            // Clone the option from the hidden option pool and append it to the dynamic select box
            sel2.appendChild(clonedOptions[i].cloneNode(true));
        }
    }
}


window.onload = function() {
            dynamicSelect("pda-brand", "pda-type");
        }