1
There is a way to prevent jQuery from using
$
if it conflicts with another library; see
jQuery in your project, you can either use the variable
jQuery
or the much shorter
$
In this text, we’ll use the
$
alias.
Including jQuery
The easiest way to include jQuery is by using a CDN:
<
script
src
=
"//code.jquery.com/jquery-2.1.4.min.js"
></
script
>
jQuery 2.x dropped support for Internet Explorer 6, 7, and 8. If you
need to support those browsers, you will have to use jQuery 1.x.
jQuery 2.x is considerably smaller and simpler because it doesn’t
need to support these aging browsers.
Waiting for the DOM to Load
The way a browser reads, interprets, and renders an HTML file is complicated, and
many an unwary web developer has been caught off-guard by attempting to program‐
matically access DOM elements before the browser has had a chance to load them.
jQuery allows you to put your code in a callback that will only be invoked once the
browser has fully loaded the page and the DOM has been constructed:
$
(
document
).
ready
(
function
() {
// code here is run after all HTML has been
// loaded and the DOM is constructed
});
It is safe to use this technique multiple times, allowing you to place jQuery code in
different places and still have it safely wait for the DOM to load. There is also a short‐
cut version that is equivalent:
$
(
function
() {
// code here is run after all HTML has been
// loaded and the DOM is constructed
});
When using jQuery, putting all of your code in such a block is a ubiquitous practice.
276 | Chapter 19: jQuery
