jQuery : Getting Started

To use jQuery, you need to include it on the pages where you wish to take advantage of it. You can do this by downloading jQuery from their website at www.jquery.com. There is usually a choice between a "Production" version and a "Development" version. The first is for your live website, because it has been minified and compressed to take up the least amount of space, which is important for your visitors, whose browser will have to download the jQuery file along with the rest of your website. For testing and development, the "Development" version is best. It hasn't been minified or compressed, so when you run into an error, you can actually see where in jQuery it happens.

Once downloaded, you will have to reference the jQuery JavaScript file on your pages, using the <script> HTML tag. The easiest way is to place the downloaded jquery.js file in the same directory as the page from where you wish to use it and then reference it like this, in the section of your document:

<script type="text/javascript" src="jquery-1.5.1.js"></script>
A part of your page should now look something like this:

<head>        <title>jQuery test</title>        <script type="text/javascript" src="jquery-1.5.1.js"></script></head>
A more modern approach, instead of downloading and hosting jQuery yourself, is to include it from a CDN (Content Delivery Network). Both Google and Microsoft host several different versions of jQuery and other JavaScript frameworks. It saves you from having to download and store the jQuery framework, but it has a much bigger advantage: Because the file comes from a common URL that other websites may use as well, chances are that when people reaches your website and their browser requests the jQuery framework, it may already be in the cache, because another website is using the exact same version and file. Besides that, most CDN's will make sure that once a user requests a file from it, it's served from the server closest to them, so your European users won't have to get the file all the way from the US and so on.

You can use jQuery from a CDN just like you would do with the downloaded version, only the URL changes. For instance, to include jQuery 1.5.1 from Google, you would write the following:
<script type="text/javascript" src="https://ajax.googleapis.com/ajax/libs/jquery/1.5.1/jquery.min.js"></script>
I suggest that you use this approach, unless you have a specific reason for hosting jQuery yourself. Here is a link to the jQuery CDN information from Google:

Read on to learn how to start using jQuery. 

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