examples/webapp/ajax/select/ajax-select.htm

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This <a target="blank" class="external" href="http://en.wikipedia.org/wiki/AJAX">AJAX</a>
example pulls the customer details for the selected customer and shows the
results without refreshing the page.

Please select one of the customers:
<p/>

<table cellspacing="8" cellpadding="8">
   <tr>
      <td> $customerSelect </td>
      <td> <div id="customerDetails"/> </td>
   </tr>
</table>

<p>&nbsp;</p>

The <a target="blank" class="external" href="http://www.prototypejs.org/">Prototype</a>
JavaScript library is used in this example. Please also see the
<a target="blank" class="external" href="http://www.prototypejs.org/learn/introduction-to-ajax">Introduction to Ajax</a>
for a good tutorial.
<p/>
This HTML page contains a customer Select control 
and a &lt;div id='<span class="st">customerDetails</span>'/&gt; element:

<pre class="codeHtml">
&lt;table cellspacing="8" cellpadding="8">
   &lt;tr>
      &lt;td> &lt;select name="customerSelect"&gt;...&lt;/select&gt; &lt;/td>
      &lt;td> &lt;div id="<span class="st">customerDetails</span>"/> &lt;/td>
   &lt;/tr>
&lt;/table>
</pre>

<p/>
When you click on the select, an HTTP request (e.g. <tt>GET ajax-select.htm?pageAction=onChangeCustomer&customerId=202</tt>)
is made to the page to get the customers details. These details are returned as HTML with a content-type of 'text/html':
<pre class="codeHtml">
&lt;table border="0" cellspacing="2" cellpadding="2">
  &lt;tr>
    &lt;td&gt;&lt;b&gt;Name&lt;/b&gt;&lt;/td&gt;
    &lt;td>Alison Smart&lt;/td&gt;
  &lt;/tr&gt;
  ...
&lt;/table&gt;
</pre>

Prototype's Ajax.Updater then updates the inner HTML of the page registered
&lt;div id='<span class="st">customerDetails</span>'/&gt; element with the HTML
content returned from the server.
<p/>
Below is the necessary JavaScript to perform the Ajax request.
<p/>
As soon as the browser DOM is loaded, Prototype's
<a target="_blank" class="external" href="http://www.prototypejs.org/api/event/observe">observe</a>
function is used to register a "<span class="green">change</span>" listener on the
"<span class="blue">customerSelect</span>" control. When you select an
option, the Ajax.Updater is invoked to retrieve the customer details and update the
target "<span class="red">customerDetails</span>" div:

<pre class="codeHtml">
&lt;html&gt;
...
&lt;body&gt;
...

  <span class="red">$</span>jsImports

  &lt;script type='text/javascript' src='<a href="/click/prototype/prototype.js">prototype.js</a>'&gt;&lt;/script&gt;

  &lt;script type='text/javascript'&gt;
    // Wait until browser DOM is loaded
    document.observe("dom:loaded", function() {

      // Observe the selected element's "change" event, which triggers the given function.
      // Note that $selector is a Velocity variable passed in from the AjaxSelect.java Page
      $('<span class="blue">customerSelect</span>').observe('<span class="green">change</span>', function(event){

        // Retrieve the source of the event, in this case the Select control
        var select = Event.element(event);

        // Ajax.Updater requests the customer for the given customerId parameter
        // and replaces the inner HTML of customerDetails div
        new <span class="maroon">Ajax.Updater</span>('<span class="red">customerDetails</span>', '<span class="blue">/click-examples/ajax/select/ajax-select.htm</span>', {
          <span class="green">method</span>: <span class="blue">'get'</span>,
          <span class="green">parameters</span>: {<span class="blue">'pageAction'</span> : 'onChangeCustomer', <span class="blue">'customerId'</span> : select.value}
        });
      });
    });
  &lt;/script&gt;
&lt;/body&gt;
&lt;/html&gt;
</pre>

The initialization code above is contained in the 
<a href="$context/source-viewer.htm?filename=ajax/select/ajax-select.js">ajax-select.js</a>
template.