JS Select options Collection

Change the items in a drop-down list depending on the selected option in another drop-down list: http://www.w3schools.com/jsref/tryit.asp?filename=tryjsref_select_options3

by js_test

HTML

<select id="car" onchange="ChangeCarList();">
    <option value="">-- Car --</option>
    <option value="VO">Volvo</option>
    <option value="VW">Volkswagen</option>
    <option value="BMW">BMW</option>
</select>
<select id="carmodel"></select>

JavaScript

var carsAndModels = {};

carsAndModels['VO'] = ['V70', 'XC60', 'XC90'];
carsAndModels['VW'] = ['Golf', 'Polo', 'Scirocco', 'Touareg'];
carsAndModels['BMW'] = ['M6', 'X5', 'Z3'];

function ChangeCarList() {
    var carList = document.getElementById("car"),
        modelList = document.getElementById("carmodel"),
        selCar = carList.options[carList.selectedIndex].value;

    while (modelList.options.length) {
        modelList.remove(0);
    }

    var cars = carsAndModels[selCar];

    if (cars) {
        for (var i = 0; i < cars.length; i++) {
            var car = new Option(cars[i], i);
            modelList.options.add(car);
        }
    }
}
window.onload = ChangeCarList;