angelzzz,
или такой формат результата - здесь переменные a и b
<!DOCTYPE HTML>
<html>
<head>
<title>Untitled</title>
<meta charset="utf-8">
<style type="text/css">
</style>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.12.0/jquery.min.js"></script>
<script>
$(function(){
var arr = [
{key:1, val:123, val2:1},
{key:2, val:223, val2:2},
{key:3, val:323, val2:2},
{key:4, val:423, val2:1}
], obj = {}, a,b;
Object.keys(arr).forEach(function (a) {
var el = arr[a];
obj[el.key] = [el.val,el.val2];
});
$("#myselect").on("change", function() {
var s = obj[this.value];
a = s[0];
b = s[1];
$("p").html(a+ " - " + b)
}).change()
})
</script>
</head>
<body>
<p></p>
<select id="myselect" >
<option>1</option>
<option>2</option>
<option>3</option>
<option>4</option>
</select>
</body>
</html>