jQuery for Web Designers
Illustration by John Hersey

Reading and changing values


From:

jQuery for Web Designers

with Joe Chellman

Video: Reading and changing values

Working in jQuery there's going to be many times when you want to find out, in your code, what the contents of something you selected are. Let's look at some ways to do that now. This page has a form, as you can see, and obviously, a lot of other HTML. So first let's look at the stuff that's not in the form. I'm just going to scroll down a little bit here, and here's my header, which I happen to know is replaced by this image over here. Let's take a look at it. So, I'm going to select the header ID, like this, and then I'm going call to the HTML method on it. This will return all the HTML inside that selected element.
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  1. 2m 17s
    1. Welcome
      1m 4s
    2. What you should know
      37s
    3. Using the exercise files
      36s
  2. 11m 59s
    1. jQuery is a JavaScript library?
      1m 15s
    2. When to use jQuery
      2m 51s
    3. Alternatives to jQuery
      1m 24s
    4. Which version of jQuery to use
      1m 50s
    5. How to install jQuery
      3m 21s
    6. Reference materials
      1m 18s
  3. 19m 19s
    1. Getting ready
      2m 26s
    2. Selecting elements to use
      3m 54s
    3. Performing multiple operations on the same line with chaining
      2m 30s
    4. Using classes to find what you're looking for
      3m 52s
    5. Adding, modifying, and removing content dynamically
      4m 3s
    6. Challenge: Form feedback
      1m 12s
    7. Solution: Form feedback
      1m 22s
  4. 18m 28s
    1. Triggering a change based on activity with event binding
      4m 37s
    2. Reading and changing values
      4m 17s
    3. Working with HTML attributes
      4m 55s
    4. Challenge: Dynamic contact form
      1m 27s
    5. Solution: Dynamic contact form
      3m 12s
  5. 16m 42s
    1. Using the Colorbox plugin to build a slideshow gallery
      4m 22s
    2. Implementing Colorbox on your site
      2m 46s
    3. Changing Colorbox options
      5m 53s
    4. Challenge: Convert to a slideshow
      1m 6s
    5. Solution: Convert to a slideshow
      2m 35s
  6. 28m 37s
    1. Using jQuery or CSS to animate elements
      2m 24s
    2. Creating simple jQuery animations
      4m 35s
    3. Animating numeric properties with animate()
      4m 56s
    4. Understanding animation easing
      4m 4s
    5. Putting it together: Flowers in the cart
      6m 4s
    6. Callbacks: What to do when the animation ends
      3m 27s
    7. Challenge: Improve the animation
      1m 3s
    8. Solution: Improve the animation
      2m 4s
  7. 4m 45s
    1. More fun plugins
      2m 38s
    2. What's next: More jQuery
      50s
    3. What's next: More JavaScript
      1m 17s

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Watch the Online Video Course jQuery for Web Designers
1h 42m Intermediate Oct 31, 2013

Viewers: in countries Watching now:

Take the next step in your web design career with jQuery, which amplifies JavaScript's power and puts a library of prebuilt functions and a diverse selection of plugins at web designers' fingertips. This course explains what jQuery is, how to install it, and use it to script more interesting, interactive websites. Author Joe Chellman will show you how to use jQuery to add web form usability, audio and video, animation, and other features like slideshow galleries to your existing HTML and CSS-based webpages.

Check out JavaScript for Web Designers for more detailed instruction on JavaScript.

Topics include:
  • What is jQuery?
  • Installing jQuery
  • Performing multiple operations with chaining
  • Using classes
  • Adding, modifying, and removing content dynamically
  • Triggering a change with event binding
  • Creating a dynamic contact form
  • Building a slideshow gallery
  • Creating simple jQuery animations
Subject:
Web
Software:
jQuery
Author:
Joe Chellman

Reading and changing values

Working in jQuery there's going to be many times when you want to find out, in your code, what the contents of something you selected are. Let's look at some ways to do that now. This page has a form, as you can see, and obviously, a lot of other HTML. So first let's look at the stuff that's not in the form. I'm just going to scroll down a little bit here, and here's my header, which I happen to know is replaced by this image over here. Let's take a look at it. So, I'm going to select the header ID, like this, and then I'm going call to the HTML method on it. This will return all the HTML inside that selected element.

Like this. If I want to strip out all that HTML and just see the text, wouldn't you know it, there's a method called text. Now, as you can see, both of these return the HTML or the text with some white space. Depending on which browser you're using you might get differing amounts of white space. This is one area that jQuery does not smooth out for you. So it also includes a trim method that can take care of that if you want, like this. And the HTML method works bidirectionally, so I can read stuff out, and I can also write stuff back in. I'm not going to use this header for now, because it's got that image over it.

Let's look at this one. I happen to know that that one has the ID of, Page ID. So, let's select that Page ID, and now I am going to set its HTML to an h1 tag that says, hi, there we go. So, you can read from or write to any element that you've selected using these methods, that's pretty handy. Now, let's switch over to the jQuery code that's at the bottom of this file And, look at working with a web form. There's is a different set of methods that are used for this application. If you have ever worked with a web form before, you know that getting values out of certain form type can be a little bit of a pain or at least different between different form types.

jQuery smoothes out a lot of that for you. So, here I'm listening for these submit event on this contact form. I'm stopping it from submitting and then I'm logging several values to the console using the val method. This will work on nearly any form element. So I'm writing out to the console the value of the name field, the email filed, the state field, which is a different field type but I just use the same method. And one great thing is that it also works on radio buttons, provided you give it a good selector. So if you're using regular JavaScript you'd have to loop over these and figure out which one is checked and only then could you get the value.

In jQuery you can use a clever selector and do it all on one line. So, in this case, I'm selecting input and I'm using the radio filter, which is built into jQuery, and then, beyond that, I'm looking for a set of radio buttons where their name is station2, which, if you look in the HTML, is what these are, and then, I'm looking for the one that's checked. And then I'm using the same val method on this multiselect, and this works on all of them. So let's check couple of things, open the console and submit this form. There we have it. All these values are coming out. And this is interesting.

I'm getting an array back from my multi-select. So, I can get all of these values, or just the one. Try this again, there we go. It's still an array, because it was a multi-select, but it just has the one item in there. And just like with the HTML and text methods, you can use val to write values back into these fields. So let's try that here in the console. Let's say I want to modify that value of that email field. Let's make it jim@example.net. I'll scroll up so you can see this and once I hit return, wowie zowie, it changes and this works on many other field types. So I can do this on the state field.

Be careful when you're doing this because you want to make sure that the value matches the actual value attributes and in this state field, I scroll up. You can see that the values are state codes, not the spelled out version. So, were going to set the value here to NJ for New Jersey, and there it is. And finally we know that we get an array out of your favorite magazine. Can we put an array back in? Let's find out. So I'm going to use square braces for my array and then I'm going to set the values, and again you need to be careful of the values that are displayed here and the ones that are shown because this is a select box again.

I know that these are all the same thing, just with the spaces removed, so I'm going to set the value to mountain biking and modern cyclist. There we go, you can also do this just with a string or a single value just like that. If you've ever worked with a check box you know that checking the value is not sufficient with a check box because the value doesn't change to checked or unchecked depending on the state of the check box. There's another way to work with check boxes that we'll look at next.

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