<label for="bootChooserControl">Boot style:</label>
<select id="bootChooserControl" name="style"></select>
<select id="colorChooserControl" name="color" disabled="disabled"></select>
<select id="sizeChooserControl" name="size" disabled="disabled"></select>
One capability of the event model that often gets ignored by many a web developer
is event bubbling. Page authors frequently focus only on the targets of events, and forget
that events will bubble up the DOM tree, where handlers can deal with those events in
more general ways than at the target level.
If we recognize that removing the option with a blank value from any of the three
dropdowns can be handled in the exact same fashion regardless of which dropdown is
the target of the event, we can avoid repeating the same code in three places by establishing
a single handler, higher in the DOM, that will recognize and handle the change
Recalling the structure of the document, the three dropdowns are contained
within a <div> element with an id of selectionsPane. We can handle the removal of
the temporary option for all three dropdowns with the following, single listener:
This listener will be triggered whenever a change event happens on any of the
enclosed dropdowns, and will remove the option with the blank value within the context
of the target of the event (which will be the changed dropdown). How slick is that?
Using event bubbling to avoid repeating the same code in lower-level handlers can
really elevate your script to the big leagues!