Demo starter files
Ok, I think I just threw a bunch of potentially new terms at you.
The DOM, or Document Object Model, is basically the same as saying the structure of the HTML. It's also often referred to as the document tree. If you haven't thought of it this way yet, visualize the HTML of a web page as a tree. The
<html> element is the root element, and each additional element is a branch, with more elements branching off as we get further into nested elements.
A library, or framework, is a large collection of functions and definitions that make a certain tasks easier to do in a given programming language. A plugin is basically the same thing, only smaller and more specific.
An analogy might be helpful here. If you're building a house, the library or framework is like a pre-constructed foundation. In fake pseudo-code let's call this "import foundation". You don't have to do any digging, and a logical size and footprint are already laid out for you, so you can get right to work building the actual house, which is much more important to you.
A plugin in this analogy would be like "import kitchen". This is a smaller, single-purpose room that comes with a pre-installed refrigerator, range, dishwasher, etc. You can still customize things like the cabinet materials and appliance colors, but again you save a lot of time by not building them yourself.
The additional benefit of using libraries, frameworks and plugins, is that they're often open source. This means lots of people have used them, and experienced people have likely contributed to making the code fast, efficient, and well documented.
- Whitespace is ignored, even more so than in HTML and CSS
;similar to CSS
- It's also case sensitive, so pay close attention when naming your own variables and functions!
Because whitespace is ignored, programmers are encouraged to space things out as much as needed to make the code readable.
We won't be stripping the whitespace from any of our code in this class, but there are a number of tools out there to minify your scripts when they're all finished. Minifying means all of the whitespace is removed, which makes the code much harder to read, but also reduces the size of the file. Computers ignore all of the white space anyway.
Most developer tools now have a "pretty-print" function which automatically formats minified script files.
A Little Background
The jQuery web site has really great documentation of everything at your fingertips using jQuery.
- Here's the starter tutorial on how jQuery works. We'll do something very similar to this together, using my demo files, to get you up and running.
- learn.jquery.com has textual explanations with sample code that can walk you through the basics and best practices.
- You'll probably spend more time referring to the API Documentation though. It has definitions of all of the methods, events, etc. available in jQuery, with simple demos showing what they do.
Great so how do we get started using it?
Actually you don't even need to download jQuery to use it. Source jQuery from the Google CDN (content delivery network).
It's free, it will often load faster than sourcing it from your own server, and many users will already have it cached in their browser thanks to other sites that use it.
The jQuery core library doesn't include all of the superfluous animation effects you might want to use though. Those are part of jQuery UI, which is an add-on library. jQuery UI includes another .js file, and a stylesheet. We will also source these from the Google CDN.
Here are some helpful terms to know when getting started, and reading the API Documentation:
- jQuery Object - the DOM element(s) you're targeting inside
- Method - a method is anything you can do with an object. jQuery has tons of methods for manipulating objects.
- Function - a chunk of code to be executed. Functions can be called right away, or defined with a name and reused later.
- Event - something that happens on the page. Mouse clicks and hovers are events.
- Event Listener - a function that is triggered when an event happens.
- Callback function - a function that executes when another function finishes.
- Chaining - One of the most powerful aspects of jQuery. Methods can be chained together to happen in sequence, similar to a callback function.
jQuery is great for very simple animations, but it has trouble with more advanced animations, and with animating lots of things at once.
CSS transitions and animations are better optimized to use the computer's GPU, and spawn separate threads for certain calculations, making them far more efficient. Don't be afraid to use jQuery to animate things! But it's a good idea to use CSS transitions if you have the option.
There are tons of jQuery plugins, but here are a few of the most popular: