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jQuery Essential Training

Making an image selector


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jQuery Essential Training

with Joe Marini

Video: Making an image selector

For the next lesson we're going to use jQuery to build an Image selector. You've probably seen these before. You've probably even built one before. Let me just open up the Groundswell_Final site so you can see what I'm talking about. So, let's go to the Lifestyle section and click on Photos. You can see that as I click on the different photos the image in the large image area changes whenever I click on one of the thumbnails. You can also see that this text down here in the caption area, that's changing as well.
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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

Making an image selector

For the next lesson we're going to use jQuery to build an Image selector. You've probably seen these before. You've probably even built one before. Let me just open up the Groundswell_Final site so you can see what I'm talking about. So, let's go to the Lifestyle section and click on Photos. You can see that as I click on the different photos the image in the large image area changes whenever I click on one of the thumbnails. You can also see that this text down here in the caption area, that's changing as well.

Now, you've probably built one of these before and they are relatively straightforward to build. But we're going to use jQuery to build one that is inherently extensible and can be accomplished in just a couple of lines of code. So, let's go build that now. Let me go back out to the file system here. So, let's go to the Start site. I'm going to open up the site in my editor. So, this is the home page. What we need to open up actually is the images page.

So, I'm going to go to the Lifestyle, and open the photos page. Okay! So, this is photos page. So, just put a design view really quick. So, here are the photos. This is the large photo right here. You can see it has an id of photo_large on it. Then is this guy here, this is the caption area. And over here are the individual thumbnails for each one of the images. So, let's go to the code view. You can see that each one of the images has an id, and an alt attribute set, and a class and so on.

So, what we're going to do is encase each one of these images in a link, so that when they are clicked on, the event will be handled by our jQuery code. So, what we're going to do is put an anchor or a link tag in front of each one of these guys, a href=, and then we'll supply a pointer to the image and then we'll close the link on each one of these guys.

So, the images are located a directory up. So, I'm going to do that and then, _images. The way the images are named, you can see that in this case it is pointing to ventura_01_thumb. The large version doesn't have this _thumb on the end. So, we're just going to copy that and scroll back and paste that in there and it's .JPG.

So, now we're going to do that with each one of these guys. So, I'm going to Copy and I'm going Paste, and Paste, and Paste. And we'll update each one of these indexes. Now, we have links that are pointing to the images. There's a couple of other things that we need to do. What we're going to do also is place a Title attribute on the link. The title is what we'll use for the caption.

So, for this title it is "Getting ready to hit Surf." And this title is "Clearly marked!" And this title is "Checkout the windsurfers in the background," and then the last title is "Winding down." Now, we've got the links wrapped around each tag.

And we've got titles on each. They'll become our captions. The idea here is if we wanted to add more thumbnails, we would just be following this convention and the jQuery code would just pick this up automatically. So, what we need to do now is write the jQuery that will actually handle these events. So, up here at the top. We are into the usual suspects. We're going to include a link to our jQuery library. We're going to say Script and the type is equal to JavaScript.

The source, I'm going to point that to jQuery library. And our jQuery library is located one directory up in scripts, and that is jQuery-1.3.2.min.js. Now, we've got the script included. What we need to do now is write our script that is going to handle the image clicking. Let's do that.

So, here is what we want to do. When the document loads, we're going to setup the event handling code to handle clicks on each of the images, and then set the large image to be the large version of the thumbnail that was clicked on. I'm going to write a jQuery function that executes when the page loads. And what we want to do is loop over all of the link tags that we just added and setup click handlers on each one of them. We only want to do this, however, for links that are enclosing images that have the Gallery class applied to them because the gallery.css style sheet indicates that it's a thumbnail in the image.

Just go down, and you'll see what I'm talking about. So, here on this image, you can see each one of these guys has a Gallery class. So, we only what to do this for links that have the Gallery class applied. So, what we're going to do is write a little jQuery to figure that out for us. So, we're going to look for links and we're going to use the jQuery has selector. Remember this is one of the content selectors I talked about. So, we're going to look for links that have image with Gallery class applied to them. And assuming we find any, we're then going to assign click handlers to each one.

The click handler is going to be a function. Inside the click handler, what we're going to do is declare a couple of variables. So, first we're going to declare a variable called largePath. We're going to point that at this. So, remember, when this function gets called it's getting called because of a click on a link. So, that this keyword will point to the link object that this applies to. So, we're going to get the attribute for the href from the link.

Then we're going to get the caption from the title. So, now we have the caption and path from an href and title. So, now what we need to do is go find that large photo and that guy should be right around here somewhere. So, down here in the mainContent. Here is the image. That's the photo_large. So, we need to set that guy.

So, we get a reference to the large photo. We're going to set its attributes. So, we're going to set the source attribute to be the largePath that we just defined. And then, we're going to set the contents of the caption element. Where is that? Caption element should be down here somewhere. Yup! There's caption1 right there. In fact, we can get rid of these other guys from the base site, because we don't need them anymore.

We're going to set the content of caption1. We're going to set its text content to be the caption that we just applied. Now, the last thing that we need to do is we don't want these links to be followed. We don't want the browser to actually try to follow the link. So, we need to return False from this event handler. That will tell the browser, don't worry about it, we've handled it. You don't need to go ahead and follow the link. And we've written the code.

Let's make sure everything looks right. Okay! Let's go back out to the browser. So, now we're going to open up the version in the Start folder. So, yup, this is the start version. Let's go to the Index page, go to the Photos. So, you can see now that as I'm clicking both the caption and the large image are changing. All right! This is extensible. So, now if I go back to the code.

Let's imagine that we added a whole bunch of new images and we'll just do a Copy and Paste. So, now if we go back to the browser and we refresh, you can see that a whole bunch of new images have been added, but it's still responding to the same event handler. We'll didn't have to update the event handler code, at all. That's using jQuery to build an image selector. Let's move on to the next example.

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


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Please wait...
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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