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jQuery Essential Training

Creating an image rotator


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jQuery Essential Training

with Joe Marini

Video: Creating an image rotator

So now that we have the accordion working, let's go build our image rotator. That's going to cause this image right here to display a nice smooth slide show through a series of images. Let's look in our folder really quick. So here we are in the folder and you can see inside the _images folder, we have a bunch of thumbnails of the photos we want to flip through. So you can see that each one has the name thumb on the end, and there is four of them.
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  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 jQuery's features
      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

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jQuery Essential Training
4h 53m Beginner Sep 01, 2009 Updated May 24, 2013

Viewers: in countries Watching now:

In jQuery Essential Training, Microsoft professional Joe Marini presents the power of the jQuery library, an open-source JavaScript project that greatly simplifies the process of adding advanced functionality to web sites. Joe teaches how to use these new features to build pages that work across browsers with the functionality that today's users (and clients) are looking for, from complex animation effects to dynamic page formatting. Joe pulls all of this together, showing how the jQuery UI plug-in can expand and streamline the capability of jQuery, and then integrating jQuery design tools into a complete sample web site. Exercise files accompany the course.

Topics include:
  • Constructing jQuery selectors and filters to gather information from web pages
  • Creating, inserting, and manipulating web page content
  • Understanding jQuery statement chaining
  • Building event handlers that work across browsers
  • Working with jQuery effects, such as showing, hiding, and fading page elements
  • Creating custom animations with specialized properties and options
  • Using the jQuery UI plug-in to give pages a polished look
Subjects:
Developer Mobile Apps Web Mobile Web Web Development
Software:
Ajax jQuery jQuery Mobile
Author:
Joe Marini

Creating an image rotator

So now that we have the accordion working, let's go build our image rotator. That's going to cause this image right here to display a nice smooth slide show through a series of images. Let's look in our folder really quick. So here we are in the folder and you can see inside the _images folder, we have a bunch of thumbnails of the photos we want to flip through. So you can see that each one has the name thumb on the end, and there is four of them.

So let's go back to our code. In the code, in the sidebar, that's this image right here. So that's the image that's currently there. What we want to do however is build a slide show around this image. So let's clean this code up a little bit right here and isolate that image. What I am going to do is put a div around this. And that's going to serve as our photo show, in fact, I am going to give it an id called photoShow.

What I am going to do now is copy and paste these images right here, so I have got the four images that we are going to loop through and each one of them is numbered in ascending order. So that's 2, that's 3, and that's 4. And for the alt, I am going to change it from that to be Photo Gallery. And I am going to do that for each one of these guys, so that we got valid alt text on each one. Let's see. We are going to leave everything else pretty much the same.

I also want to do something else, I want to make sure that each one of these images is clickable so that when the user clicks on the image, they go to the photo's home page of the lifestyle section. So I am going to put in link and I am going to say a href="lifestyle/photos.htm", and let's see that should be about it. And I am going to take off that thing there, put on to the image.

So now I am going to do that for each one of these guys. Copy, paste, paste, paste and the closing links. So now I have got links around each one of the images, so what I need to do now is build the rotator. And to do that, before I actually build the code for the rotator, what I am going to do is define some CSS that will help me. Now the CSS that I am going to write is going to do a couple of things. It's going to position the images so that they are all underneath each other, and I am gong to define some z-index information so that the images appear to bubble up from underneath each other.

Let's go to the sidebar section, and I believe the sidebar is down here somewhere. So here we are in the sidebar section, so what I am going to do is define a couple of style sheets, go a little down here. So down here, the first thing I am going to do is define a style for my photoShow div. So my photoShow is going to have a style sheet that does a couple of things. First, I am going to set the position to be relative. Then I am going to define a height and a width that encapsulates the images.

So the height is going to be 190 pixels because that's how big the images are, and the width will be 240 pixels because that's how wide the images are. And then I am going to set the margin left to be auto, this way it correctly positions itself inside that sidebar div. Now that I have defined a style sheet for the containing div, I am going to define another style sheet, this time it's going to be for the div that's inside the photoShow.

Remember, this encapsulates all the images, and each image now is going to be encapsulated in a div as well. I am going to write that the position is absolute, and I am going to set the z-index of each image to be 0. Let's go back to the code. So here's the div for the photoShow and what I am going to do is I am going to wrap each link and image pair inside a separate div.

Because these divs are going to be what we are hiding and showing to the user. So I am going to do it for that one, and I am going to do it for that one, and for that one, and for that one. And I will close each one off correctly. There is that one, there is that one, and there is that one. Now let's go back to the CSS. So now I have defined style sheets for both the containing divs and for the divs that wrap each one of the images. So I am going to write a couple more style sheets now that help me position the images properly, so when they are animated they show up correctly in the stack order.

Right now it's photoShow, and this is going to be for the div that I am going to give a class of previous. And for the previous one, I am just going to give that a z-index, index of 1. And for the same thing I am going to call this the current image and that's going to have a z-index of 2. So what this is going to do is cause whichever image has the current style sheet to appear on top of all the others, and the one that has previous is going to appear directly underneath it.

So all I need to do now is make sure that the first image starts off with the correct style sheet applied. So let's go back to the code and we'll give this guy here, the class of current. He is going to start out on top and all the other images will start out underneath that one. Now it's time to simply go write the animation code, but before we do that let's go out to the browser. And let's refresh, and you can see that so far there is no visible changes but there are four images there.

And they are all stacked up underneath each other. So now let's write the rotation code. Okay, back to the code. So once again, we want this to happen on the document.ready, so I am just going to put that function in here as well. So let's write the code now that's going to cause each one of the images to rotate. What I am going to do is call the JavaScript setInterval() function and I am going to write a little routine called rotateImages, so this will be called.

And let's call it every two seconds. So the value of 2000 is 2000 milliseconds which is 2 seconds. Now we need to write the function for rotateImages, and what we are going to do first is get the current photo. The current photo is going to be the result of a jQuery operation. That's going to get me the photoShow's current div. Okay, so that's going to get me whichever div has the current class.

Then we are going to get the next photo, this is the photo that we are going to fade too. And that's going to be whatever the current photo's next, remember using our traversal knowledge from earlier in the course. This is going to get the next div that's in line. If we are at the last div, that's not going to be existent, so we need to catch that case. So if it turns out that the next photo's length and remember this tells us how many items were in that jQuery array.

The length of that is 0, then we have reached the last div. So what we need to do then is say well, okay in that case, the next photo is equal to just the first photo. So we are drawing again on our jQuery knowledge, we are just going to go ahead and retrieve the photoShow's first child using the first filter right here. And this will get us the first div that's inside the photoShow. So now that we have got the right photos that we are going from and to, let's use a little statement chaining to do some animation.

So we are going to tell the current photo, we are going to remove the current class from our CSS section and we are going to add a class, we are going to add previous. So this will cause whichever photo was current to drop down one level in the z-index order. Then we are going to tell the photo that's next that we are going to set its CSS property, we are going to set its opacity to 0.

Then we are going to add a class, and we are going to make this one the current photo. And we are going to animate the opacity using our basic animation function. We are going to animate the opacity up to 1.0 over a duration of 1 second, and we want to declare a callback() function. Remember the callback() function feature of this.

The callback() function will tell the current photo to remove its previous class. So that way the next photo after that will pop-up in the order. So after we have done that, we are ready to save, and now we should have our image rotator working. Let's go ahead and switch back out to the browser, let's refresh. So now you can see that every two seconds what's happening is each div is now animating its opacity and fading up in front of the image in front of it.

So each image here, whichever one is current, drops down below the one that's next. The one that's next is set to opacity of 0, so it's practically invisible. And then it fades up in front of the image in front of it. That is the image rotator in jQuery.

Find answers to the most frequently asked questions about jQuery Essential Training.


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Q: When attempting to download jQuery, as the author does in the movie “Downloading and installing jQuery,” the file does not download. When any of the links on the download page are clicked, the browser opens a page of code instead.
A: This sometimes happens when a web browser doesn't have the proper MIME type to prompt the user to download the file instead of open it directly. Therefore, the browser is opening the code instead of downloading it. If this occurs, download the file on a by Control-clicking (Mac) or right-clicking (Windows) on the download link and choosing the Save File option, which will download it to the computer.
Q: Why do some of the examples use the form $("document") instead of just $(document)?
A: jQuery's $(document).ready() function will work with either form. As a reminder, you can also just use the $() shorthand to accomplish the same thing:
 
$(function() {
// code to run when the document is ready
});
Q: I am stuck on the first exercise in Chapter 1, video 3 "Creating a simple jQuery enabled page".

Your example javascript code, both in the movie and in the exercise files,
reads as follows:

<script type="text/javascript">
$("document").ready(function() {
alert("The page just loaded!");
});
</script>

This is not working for me.
A: After jQuery 1.3.2, a change was made where quotes were no
longer needed around the "document" argument to the jQuery $() function.

Type the following instead.

<script type="text/javascript">
$(document).ready(function() {
alert("The page just loaded!");
});
</script>
Q: How do I remove the resize handle that appears on on <textarea> elements in some browsers, such as Firefox and Chrome?
A: Some browsers automatically provide this feature for these text elements. You can disable this feature using CSS by providing a style rule for the element that specifies no resize behavior. Add the rule "resize: none;" to a stylesheet that is applied to the textarea, and the resize handle will not appear.

Q: This course was updated on 5/24/2013. What changed?

A: This update includes a new chapter on the jQuery AJAX features, new movies on associating data with page elements, and updates to the chapters on events and the jQuery UI plugin to reflect changes in JQuery 1.8.
Q: In Chapter 7, for the "Using the Resizable effect" movie, the example code from the Groundswell_Final and Groundswell_Start folders isn't limiting the width of the window. What should I do?
A: There's a bug in the example file. You need to add: 
textarea { resize:none;}

to the main.css file in the _css folder, and change the link tag in register.htm from:

<link href="../_css/sunny/jquery-ui-1.7.2.custom.css" rel="stylesheet" type="text/css" media="screen, projection" />

to

<link href="../_css/sunny/jquery-ui-1.10.2.custom.css" rel="stylesheet" type="text/css" media="screen, projection" />

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