At the Forge - Dojo Events and Ajax
We can then tell the user's browser to invoke our openAlert function whenever someone clicks on a paragraph of text:
<p onclick="openAlert();">This is a paragraph.</p>
Second, event handlers sometimes can be used in contexts you might not expect. For example, the above <p> tag has an onclick handler. You normally wouldn't think of clicking on a paragraph of text, but we can do that. This is the basis for some of the modern drag-and-drop events.
As a simple example, let's see how we might implement our onclick handler from before using Dojo events. First, we need to modify our event-handling function so that it takes one argument, the event itself:
Next, we must connect the paragraph to the event. Rather than doing this directly, by setting the onconnect handler, we give our paragraph an id tag:
<p id="para">This is a paragraph.</p>
Now, we can use Dojo's dojo.byId function—similar in some ways to Prototype's $() function—to get the node itself:
var para = dojo.byId("para");
Finally, we connect our paragraph to the handler function we created:
dojo.event.connect(para, "onclick", openAlert);
If we put it all together, we get the program shown in Listing 1, which I have called test-dojo.html.
Listing 1. test-dojo.html
If you load the page into a browser window, you will see that it works just like the previous version. Given that this version is more complex, it might not seem obvious how it is better.
Webinar: 8 Signs You’re Beyond Cron
On Demand NOW
Join Linux Journal and Pat Cameron, Director of Automation Technology at HelpSystems, as they discuss the eight primary advantages of moving beyond cron job scheduling. In this webinar, you’ll learn about integrating cron with an enterprise scheduler.View Now!
- When Official Debian Support Ends, Who Will Save You?
- Ubuntu Ditches Upstart
- May 2015 Issue of Linux Journal: Cool Projects
- Video On Demand: 8 Signs You're Beyond Cron
- Picking Out the Nouns
- "No Reboot" Kernel Patching - And Why You Should Care
- DevOps: Better Than the Sum of Its Parts
- Return of the Mac
- Drupageddon: SQL Injection, Database Abstraction and Hundreds of Thousands of Web Sites