Untitled

<!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <title></title>
</head>
<body>
  <form id="picker" action="" method="post">
    <select id="state">
      <option value="">--</option>
      <option value="MO">Missouri</option>
      <option value="WA">Washington</option>
      <option value="CA">California</option>
    </select>
    <select id="cities">
    </select>
  </form>

<script>
  var citystore = new Array();
  citystore[0] = ["CA", "San Francisco"];
  citystore[1] = ["CA", "Los Angeles"];
  citystore[2] = ["CA", "San Diego"];
  citystore[3] = ["MO", "St. Louis"];
  citystore[4] = ["MO", "Kansas City"];
  citystore[5] = ["WA", "Seattle"];
  citystore[6] = ["WA", "Spokane"];
  citystore[7] = ["WA", "Redmond"];

  window.onload = function() {
    document.getElementById("state").onchange = filterCities;
  };

  function filterCities() {
    var state           = this.value;
    var city            = document.getElementById("cities");
    city.options.length = 0;

    for (var i = 0; i < citystore.length; i++) {
      var st = citystore[i][0];

      if (st == state) {
        var opt = new Option(citystore[i][1]);
        try {
          city.add(opt, null);
        } catch (e) {
          city.add(opt);
        }
      }
    }
  }
</script>
</body>
</html>