Another great feature for the a4j:param component is the ability to use JavaScript to assign the 'value' attribute. In this case the 'noEscape' attribute should be set to true. When noEscape="true", the 'value' can contain any JavaScript expression or JavaScript function. This will be executed and the result will be sent to the server as the value of a4j:param.

The following example demonstrates how to assign the backing bean with browser screen size values.