Selectors are the most basic and fundamental part of jQuery. They are really what makes jQuery such an awesome framework and worth using. If you are familiar with CSS, you already know how to use selectors, you just don't know that you do.
What is a selector? To put it simply, it is a "$()". A dollar-sign and a parenthesis. To be more precise it is what is in the parenthesis that makes up the selector. Another way to think of a selector is a shortcut to calling "document.getElementById('elementId');" or "document.getElementByClass('classId');".
Just like coding css, jQuery selectors use an '#' for an 'id', and a '.' for a 'class'. So "#div1" is really the same as typing document.getElementById("div1");. Another important thing to note is that you can use XPATHs to get (read select) what you want, I haven't done that here, but it is an available option.
Here is some sample code to play with.
<div id="div1">
Content for first div
</div>
<div id="div2">
Content for second div
</div>
Lets say you need to adjust the background of the first div. To get started you need to select it (build a selector).
$(document).ready(function(){
$("#div1")
});
The line $("#div1") selects the first div. Now that you have it selected you can do something with it. Lets change the background color... you know, just for fun, or if you need a real excuse, maybe you are changing the background to draw attention to it.
$().ready(function(){
$("#div1").css("background","#000099");
});
Running the above code will take the div with the id of "div1" and change the css so the background color is now #000099. Look at the "Sandbox" on the right to see an example of this code in action.
Karl Swedberg is one of the jQuery all-stars (not entirely true, but the guy does rock at jQuery, and has written two books on how to use jQuery) and has set up a fantastic lab that was then 'enhanced' by Cody Lindley. Head on over to http://codylindley.com/jqueryselectors/ to check out the lab and play with jQuery selectors in a much bigger sandbox than the one here.
