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Multi Level Drop Down Category & Subcategory Hierarcheal Selection using JavaScript

This code will enable you to populate the list of states depending on the country selection. For example if you choose United States in the country drop down selection, the state drop down will contain Alaska, California etc. Else if you choose Canada, the state drop down list will contain Alberta, British Columbia etc.

All of this is done without reloading the page. This script could also be used in other formats, e.g., automobiles: type/make/model; or books: publisher/author/title. In order implement this script, perform the instructions below:

Create a file called countryStateCity.js and add the following code to the countryStateCity.js file.

 CODE

/* Created by: Michael J. Damato | http://developing.damato.net/ */
// State lists
var states = new Array();

states['Canada'] = new Array('Alberta','British Columbia','Ontario');
states['Mexico'] = new Array('Baja California','Chihuahua','Jalisco');
states['United States'] = new Array('California','Florida','New York');

// City lists
var cities = new Array();

cities['Canada'] = new Array();
cities['Canada']['Alberta']          = new Array('Edmonton','Calgary');
cities['Canada']['British Columbia'] = new Array('Victoria','Vancouver');
cities['Canada']['Ontario']          = new Array('Toronto','Hamilton');

cities['Mexico'] = new Array();
cities['Mexico']['Baja California'] = new Array('Tijauna','Mexicali');
cities['Mexico']['Chihuahua']       = new Array('Ciudad Juárez','Chihuahua');
cities['Mexico']['Jalisco']         = new Array('Guadalajara','Chapala');

cities['United States'] = new Array();
cities['United States']['California'] = new Array('Los Angeles','San Francisco');
cities['United States']['Florida']    = new Array('Miami','Orlando');
cities['United States']['New York']   = new Array('Buffalo','new York');

function setStates() {
  cntrySel = document.getElementById('country');
  stateList = states[cntrySel.value];
  changeSelect('state', stateList, stateList);
  setCities();
}

function setCities() {
  cntrySel = document.getElementById('country');
  stateSel = document.getElementById('state');
  cityList = cities[cntrySel.value][stateSel.value];
  changeSelect('city', cityList, cityList);
}

function changeSelect(fieldID, newOptions, newValues) {
  selectField = document.getElementById(fieldID);
  selectField.options.length = 0;
  for (i=0; i<newOptions.length; i++) {
    selectField.options[selectField.length] = new Option(newOptions[i], newValues[i]);
  }
}

// Multiple onload function created by: Simon Willison
// http://simonwillison.net/2004/May/26/addLoadEvent/
function addLoadEvent(func) {
  var oldonload = window.onload;
  if (typeof window.onload != 'function') {
    window.onload = func;
  } else {
    window.onload = function() {
      if (oldonload) {
        oldonload();
      }
      func();
    }
  }
}

addLoadEvent(function() {
  setStates();
});

Add the following code in the Head section of your web page:

 CODE
<script type="text/javascript" src="countryStateCity.js"></script>

Add the following code to the body section of your web page:

 CODE
<fieldset style="width: 230px;">
<legend><strong>Make your selection</strong></legend>
<p>
<form name="test" method="POST" action="processingpage.php">
<table>
<tr>
<td style="text-align: left;">Country:</td>
<td style="text-align: left;">
<select name="country" id="country" onchange="setStates();">
  <option value="Canada">Canada</option>
  <option value="Mexico">Mexico</option>
  <option value="United States">United States</option>
</select>
</td>
</tr><tr>
<td style="text-align: left;">State:</td>
<td style="text-align: left;">
<select name="state" id="state" onchange="setCities();">
  <option value="">Please select a Country</option>
</select>
</td>
</tr><tr>
<td style="text-align: left;">City:</td>
<td style="text-align: left;">
<select name="city"  id="city">
  <option value="">Please select a Country</option>
</select>
</td>
</tr>
</table>
</form>
</fieldset>

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