- What is jQuery? 3:10
- jQuery: History and Relevance Today 2:51
- jQuery vs. JavaScript 6:02
- Review: What is jQuery? 5 questions
- Animating Elements with jQuery 7:43
- jQuery Syntax and Animation Effects 2 objectives
- Blog Previewer: Changing Content Inside Elements 7:13
- Using text() and html() 3 objectives
- Blog Previewer: Getting Values from Form Fields 6:06
- Getting Values from Form Fields 2 objectives
- Introduction to jQuery Review 5 questions
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Animating Elements with jQuery
7:43Create simple, fun animation sequences with jQuery!
jQuery offers many methods that can
help you easily manipulate the DOM.
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Manipulating DOM elements can include
adjusting an element's visibility
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as we've already seen with the hide
method, as well as adding, deleting, or
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modifying the contents or attributes of an
element and changing an element's styling.
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One area where jQuery
really shines is animation.
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There are several built-in methods that
allow you to use fun animations when you
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add, remove, or
reveal elements on a webpage.
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There's fadeIn and
Out which changes the opacity over time.
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You can literally see through the element
as it disappears or comes into view.
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slideDown() and slideUp() reveal
an element with a sliding motion.
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There's even a method called delay()
which lets you add a delay between two
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animations.
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For our first jQuery project,
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we'll use a few of these methods
to build a simple blog previewer
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with a flash message that appears
when the PREVIEW button is pressed.
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We won't actually be
building a functioning blog.
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That would require back end programming,
a database to store blog entries, and
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a lot of complex functionality
like user accounts
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that are beyond the scope of this course.
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Our project will simply allow the user to
preview what their blog entry will look
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like and
let them know the changes have been saved.
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Think of it as a prototype or
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demonstration of a feature you'd add
to a larger, more complex project.
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In this video,
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we'll create a flash message to learn
about animation methods in more detail and
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see how they can be used together
to create some pretty cool effects.
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A flash message is designed to show
a temporary message like a warning,
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confirmation, or alert to a user.
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Since the message is only
a temporary notification,
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we wanna show it when the page loads
then hide it after a few seconds delay.
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Later, we'll program the message so
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that it only displays once a user
clicks this PREVIEW button.
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But for now, the message and animation
will show each time the page is refreshed.
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Firstly, open up the workspace with
this video to follow along with me.
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If you'd rather work with your own text
editor, you can download the files for
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this course below.
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Here we have got an index.html file,
an app.js file, and
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a CSS folder,
which we won't be doing anything with but
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it's providing some styles to make
the blog previewer page look nice.
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I've already included the file
you'll need to use jQuery as well.
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Once again,
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I will show you how you can add jQuery to
your own projects later on in this course.
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Go ahead and go to app.js because
we're all ready to start coding.
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If we look at the index.html file,
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we can see there’s a div at the top
with an ID of flash message.
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In app.js, we’ll use the ID selector
to select the flash message element.
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Be sure to include the hash symbol
as we’re selecting an ID this time.
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Let's make the message fade into view.
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That means that first we need to hide
the message when the page loads.
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Let's save and refresh the preview to
make sure it's hidden, it is, great.
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Then we'll use a jQuery animation
effect to fade it into view.
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Let's try the fadeIn animation.
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So let's save and preview the page.
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As you can see, the message fades in
quite quickly, only 400 milliseconds.
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That's because all jQuery animations
last for 400 milliseconds by default.
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However, you can alter the time by passing
in a value to the jQuery animation method.
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To make the fade effect more obvious,
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let's fade the message
in over two seconds.
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To do that,
we'll pass 2,000 to the fadeIn method.
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There are 1,000 milliseconds
in each second.
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So 2,000 milliseconds is two seconds.
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Let's save and refresh the preview.
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And the message is now
appearing more slowly.
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Two seconds seems a bit too slow.
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Let's change it to 1,000 milliseconds,
or one second.
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And that's better.
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Now we wanna make the flash
message disappear.
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Let's use the slideUp method for that.
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Save the file and refresh the preview.
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We'll see the message appear and
disappear.
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It's a nice animiation but
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we aren't really allowing the user
enough time to read the message.
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We need to delay the animiation.
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jQuery has a delay method that
waits a given amount of time and
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then moves up to the next animation.
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I'm going to sandwich in a delay
call between fadeIn and slideUp.
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Let's give the user three
seconds to read the message and
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then slide the message out of view.
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Save and preview.
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The message fades in, we wait three
seconds, and it disappears, awesome.
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Instead of fadeIn,
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let's use slideDown as that animation is
complementary to the slide up animation.
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Save and preview.
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And that's looking pretty good.
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We can get the same effect in even
less code, jQuery let's you string or
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chain together methods
on the same element.
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In other words, you can chain all
the methods together like this.
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Writing the code like
this is more readable and
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saves us from having to select the flash
message div over and over again.
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We can see that we select the flash
message, hide it immediately,
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then reveal the message with a slideDown,
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wait three seconds, and
then slide the message back up.
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How does this work?
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Most jQuery methods return the same
element each time they're called.
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So when the hide method is called on the
flash message, jQuery hides the element,
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then returns a reference to that element.
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So calling slideDown next applies that
animation to the message element as well.
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You can think of it a bit
like a factory line.
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jQuery grabs the element from the page and
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passes it down the line where
each method does something to it.
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Chaining is a nice feature of jQuery
that makes your code easier to read and
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write but it can also get out of hand and
lead to long lines of code.
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If a line of jQuery is getting too long,
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you can add a new line at
every method like this.
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Indenting the method under the element
you're performing actions on
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helps with readability as well.
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Feel free to play around with this and
experiment with different animations and
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delay times and see what fun animation
sequences you can come up with.
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As you just saw it, jQuery has some really
nice animation methods that can add
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a little flair to the user
experience of your pages.
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In a short amount of time and
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with a relatively small amount of code,
we performed a complex animation sequence.
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You also saw how to write more
concise code with method chaining.
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You may now be starting to understand why
jQuery's motto is write less, do more.
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