Easy-to-follow video tutorials help you learn software, creative, and business skills.Become a member

Using global AJAX event handlers

From: jQuery Essential Training

Video: Using global AJAX event handlers

The jQuery AJAX library provides a set of global AJAX event handlers that you can use to register functions to listen in for interesting events that take place during the lifecycle of an AJAX request on a given page. Here in the API documentation let's go ahead and click on the global AJAX event handlers, and you can see that there is about a half dozen functions that you can use to register events for when something interesting happens in an AJAX request. Now again, these are not functions that you call; these are functions that get called for you.

Using global AJAX event handlers

The jQuery AJAX library provides a set of global AJAX event handlers that you can use to register functions to listen in for interesting events that take place during the lifecycle of an AJAX request on a given page. Here in the API documentation let's go ahead and click on the global AJAX event handlers, and you can see that there is about a half dozen functions that you can use to register events for when something interesting happens in an AJAX request. Now again, these are not functions that you call; these are functions that get called for you.

And so for example, you use the AJAX send function to register an event handler that gets called when an AJAX request is about to be sent. And again, these are global, so these are for all of the AJAX requests on your page. So for example, you might use the ajaxStart and ajaxComplete events to show some kind of user interface on your webpage to let the user know that there is an AJAX request taking place, and that they need to be patient while data is retrieved from the server.

You might use, for example, the ajaxError event handler to centralize all of your error handling rather than attach individual error functions to each one of your requests. Let's take a look at these events in action. We're going to jump over to the code here, and here in my code I've got Globals_Finished up in my editor, and that's this file right here. So you can see that I've got a whole bunch of functions. There is Start. There is Stop. There is Send, Complete, Error, and Success.

So I've registered functions, and basically what I am doing in each one of these functions is just using the developer console to log some message about something happening with AJAX. And then after all of these global event handlers have their functions registered, I call this get data function right here. And getData, all it's doing is using the get shorthand method to get the testdata.txt file, which we've been using in this chapter, and there is a successFn right here. And in the successFn we just simply log out that the result is being set, and we put the contents of the result parameter right here, into this content paragraph right here.

So let's save that. Let's bring this up in the browser, and let's see what happens. So I am going to run this in my local server. So you can see that "This is some text data." got set into that paragraph. Let's bring up the Developer Tools, and let's switch over to the Console, and you can see that in the order in which things happened, each one of those event handlers put out a little string to the Developer Console. So right here we have AJAX is starting and then it says About to request data and then Setting the result and then it says Looks like everything worked! Everything's finished! The AJAX request ended.

And if we go back to the code--let's scroll up-- you can see that those strings correspond to each one of these functions. So for ajaxStart it says AJAX starting, and then ajaxStop it says AJAX request ended and so on and so forth. Using these global event handlers, you can register events that will get called for every single AJAX request. In fact, let's take a look at what happens when an error occurs, and we have our ajaxError handler right here. And this function takes some parameters. So do the other ones as well, but they're optional, and I'm not using them in this example.

But here in the case of ajaxError, we have parameters for the event, the jqXHR object, any of the AJAX settings, and the actual error that happened. So let's scroll down, and make a request for a file that we know doesn't exist, right. So testdata1.txt is not real, so let's save that and then let's go back to the browser, and now let's refresh the page, and you can see that it didn't work. When we bring up the Developer Tools, right here we have our AJAX starting. It says About to request data, but then you could see that there was an error.

It seems like requesting testdata1.txt was a problem. If we expand that out, we can see that there was a whole bunch of things that took place in here, right, and then it says, Hmmm. seems that there was a problem and then not found. But you can still see that Everything's finished! and AJAX request ended functions still completed. So let's go back to the code. In this case, rather than the ajaxSuccess function being called that says looks like everything worked, this time the AJAX error function got called and it says Hmm.

Seems Like there was a problem, and the not found message is passed in by jQuery as the error of why things went wrong. These global event handlers in many ways provide some nice centralization of AJAX functionality so that you can provide some really great user experience to your users like global settings of showing when requests are in progress, or centralized error handling, and it really makes working with AJAX and jQuery a lot easier.

Show transcript

This video is part of

Image for jQuery Essential Training
jQuery Essential Training

49 video lessons · 95768 viewers

Joe Marini
Author

 
Expand all | Collapse all
  1. 2m 52s
    1. Welcome
      1m 9s
    2. Using the exercise files
      1m 43s
  2. 17m 37s
    1. What is jQuery?
      5m 19s
    2. Downloading and installing jQuery
      2m 20s
    3. Creating a simple jQuery-enabled page
      7m 12s
    4. Overview of features in jQuery
      2m 46s
  3. 59m 57s
    1. Overview of selectors and filters
      2m 9s
    2. Using basic jQuery selectors
      9m 6s
    3. Using basic jQuery filters
      8m 35s
    4. Using jQuery attribute filters
      6m 7s
    5. Child, visibility, and content filters
      9m 59s
    6. Form selectors and filters
      9m 3s
    7. Traversing documents
      9m 1s
    8. Understanding jQuery statement chaining
      1m 42s
    9. Practical example 1: Annotating page links
      4m 15s
  4. 47m 16s
    1. Creating, getting, and setting content
      5m 53s
    2. Manipulating attributes
      5m 43s
    3. Inserting content
      4m 57s
    4. Wrapping, replacing, and removing content
      5m 27s
    5. Working with CSS
      6m 19s
    6. Associating data with page elements
      9m 30s
    7. Practical example 2: Automatic TOC generator
      9m 27s
  5. 33m 6s
    1. Understanding the jQuery event handling features
      2m 4s
    2. Binding and unbinding events
      6m 23s
    3. Convenient event helper methods
      4m 40s
    4. Using the jQuery event object
      6m 21s
    5. Using miscellaneous event features
      4m 38s
    6. Practical example 3: Table striping and highlighting
      9m 0s
  6. 28m 45s
    1. Hiding and showing elements
      5m 23s
    2. Fading elements in and out
      4m 2s
    3. Sliding elements
      4m 3s
    4. Creating custom animations
      5m 58s
    5. Practical example 4: Image rotator
      9m 19s
  7. 25m 30s
    1. Introduction to jQuery UI
      3m 40s
    2. Exploring the jQuery UI widgets
      5m 24s
    3. Exploring the jQuery UI effects
      3m 58s
    4. Using the jQuery UI ThemeRoller
      4m 11s
    5. Downloading and installing jQuery UI
      8m 17s
  8. 47m 49s
    1. Overview of the sample web site
      3m 50s
    2. Using the accordion widget
      9m 14s
    3. Creating an image rotator
      10m 22s
    4. Building hover tooltips
      7m 26s
    5. Making an image selector
      9m 30s
    6. Using the Resizable effect
      7m 27s
  9. 30m 2s
    1. Working with Asynchronous JavaScript and XML (AJAX)
      10m 8s
    2. Using AJAX helpers
      4m 34s
    3. Understanding AJAX data types
      10m 14s
    4. Using global AJAX event handlers
      5m 6s
  10. 20s
    1. Goodbye
      20s

Start learning today

Get unlimited access to all courses for just $25/month.

Become a member
Sometimes @lynda teaches me how to use a program and sometimes Lynda.com changes my life forever. @JosefShutter
@lynda lynda.com is an absolute life saver when it comes to learning todays software. Definitely recommend it! #higherlearning @Michael_Caraway
@lynda The best thing online! Your database of courses is great! To the mark and very helpful. Thanks! @ru22more
Got to create something yesterday I never thought I could do. #thanks @lynda @Ngventurella
I really do love @lynda as a learning platform. Never stop learning and developing, it’s probably our greatest gift as a species! @soundslikedavid
@lynda just subscribed to lynda.com all I can say its brilliant join now trust me @ButchSamurai
@lynda is an awesome resource. The membership is priceless if you take advantage of it. @diabetic_techie
One of the best decision I made this year. Buy a 1yr subscription to @lynda @cybercaptive
guys lynda.com (@lynda) is the best. So far I’ve learned Java, principles of OO programming, and now learning about MS project @lucasmitchell
Signed back up to @lynda dot com. I’ve missed it!! Proper geeking out right now! #timetolearn #geek @JayGodbold
Share a link to this course

What are exercise files?

Exercise files are the same files the author uses in the course. Save time by downloading the author's files instead of setting up your own files, and learn by following along with the instructor.

Can I take this course without the exercise files?

Yes! If you decide you would like the exercise files later, you can upgrade to a premium account any time.

Become a member Download sample files See plans and pricing

Please wait... please wait ...
Upgrade to get access to exercise files.

Exercise files video

How to use exercise files.

Learn by watching, listening, and doing, Exercise files are the same files the author uses in the course, so you can download them and follow along Premium memberships include access to all exercise files in the library.


Exercise files

Exercise files video

How to use exercise files.

For additional information on downloading and using exercise files, watch our instructional video or read the instructions in the FAQ.

This course includes free exercise files, so you can practice while you watch the course. To access all the exercise files in our library, become a Premium Member.

Join now "Already a member? Log in

Are you sure you want to mark all the videos in this course as unwatched?

This will not affect your course history, your reports, or your certificates of completion for this course.


Mark all as unwatched Cancel

Congratulations

You have completed jQuery Essential Training.

Return to your organization's learning portal to continue training, or close this page.


OK
Become a member to add this course to a playlist

Join today and get unlimited access to the entire library of video courses—and create as many playlists as you like.

Get started

Already a member?

Become a member to like this course.

Join today and get unlimited access to the entire library of video courses.

Get started

Already a member?

Exercise files

Learn by watching, listening, and doing! Exercise files are the same files the author uses in the course, so you can download them and follow along. Exercise files are available with all Premium memberships. Learn more

Get started

Already a Premium member?

Exercise files video

How to use exercise files.

Ask a question

Thanks for contacting us.
You’ll hear from our Customer Service team within 24 hours.

Please enter the text shown below:

The classic layout automatically defaults to the latest Flash Player.

To choose a different player, hold the cursor over your name at the top right of any lynda.com page and choose Site preferencesfrom the dropdown menu.

Continue to classic layout Stay on new layout
Exercise files

Access exercise files from a button right under the course name.

Mark videos as unwatched

Remove icons showing you already watched videos if you want to start over.

Control your viewing experience

Make the video wide, narrow, full-screen, or pop the player out of the page into its own window.

Interactive transcripts

Click on text in the transcript to jump to that spot in the video. As the video plays, the relevant spot in the transcript will be highlighted.

Are you sure you want to delete this note?

No

Your file was successfully uploaded.

Thanks for signing up.

We’ll send you a confirmation email shortly.


Sign up and receive emails about lynda.com and our online training library:

Here’s our privacy policy with more details about how we handle your information.

Keep up with news, tips, and latest courses with emails from lynda.com.

Sign up and receive emails about lynda.com and our online training library:

Here’s our privacy policy with more details about how we handle your information.

   
submit Lightbox submit clicked
Terms and conditions of use

We've updated our terms and conditions (now called terms of service).Go
Review and accept our updated terms of service.