<select onchange="getRow(this.value)" id="parent" name="parent">
<option disabled="disabled" selected="selected">Выбор авто</option>
<option value="vaz">ВАЗ</option>
<option value="opel">Opel</option>
<option value="bmw">BMW</option>
</select>
<br />
<select onchange="getMark(this)" id="child" name="child"></select>
<script type="text/javascript">
child = document.getElementById('child');
child.style.display = 'none';
function getRow(type){
var auto = new Array();
auto['vaz'] = ['2106','2109','2103'];
auto['opel'] = ['Astra','Antara','Corsa', 'Corsa OPC 2011'];
auto['bmw'] = ['BMW X1','BMW X3','BMW X5', 'BMW Z4'];
var count = auto[type].length;
for(key in auto[type]){
console.log(auto[type][key]);
var opt = document.createElement('option');
opt.value = auto[type][key];
opt.innerHTML = auto[type][key];
child.appendChild(opt);
}
child.style.display = 'block';
}
function getMark(select){
alert('Selected: '+select.value);
}
</script>
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