Great news! O'Reilly has been kind enough to let me distribute my eBook Unobtrusive Ajax to readers of my blog, so now you can download and read it for free!

Download "Unobtrusive Ajax" eBook

From the book's cover:

Unobtrusive Ajax is about making web applications that work for everyone all the time, even if you have JavaScript turned off, or you're using a mobile phone or a screen reader, or however you happen to be using the Web. It's about the separation of behavior (JavaScript), content (HTML), and presentation (CSS).

This short cut will focus on the practical benefits of using Ajax and JavaScript unobtrusively and show you that unobtrusive web development and progressive enhancement benefit both web developers and users of the Web. You'll get to see many simple examples of building web interfaces that are unobtrusive. You'll quickly see that it is actually very easy to make web applications that everyone can use.

When you're finished reading this book, you will be able to convince anyone why developing unobtrusively is the best way to build a site with JavaScript and Ajax.

I wrote this book back in 2007, before I'd discovered jQuery, so writing unobtrusive JavaScript has become even easier than ever. That said, the principals of writing web pages that work without JavaScript remain the same: keep your content in the HTML, use real links and forms, and avoid depending on JavaScript or Flash for any critical functionality.

Nowadays, I would also suggest bearing different user interfaces in mind. Not every visitor to your website has a mouse and a keyboard, some are using their handheld touchscreen phones, and if your shopping cart requires people to drag and drop, you may end up losing customers. Be careful not to make assumptions about your visitors. If you stick with basic HTML, you can't go wrong.

jQuery announced that they are now officially supporting jQuery Templates, thanks in big part to Microsoft.

Templating cleans up the job of generating HTML with jQuery. It also gives you the opportunity of keeping HTML code out of your JavaScript completely, if you wish.

Let's say you have a block of data like this:

var fruits = [
    { name: 'apples', color: 'green' },
    { name: 'oranges', color: 'orange' },
    { name: 'bananas', color: 'yellow' },
    { name: 'tomatoes', color: 'red' }
];

You want to display the data in a nice table with some color effects:

Without templates, your code might look like this:

// create a table
var $table = $('<table class="fruit-table">');

// append a header to the table
$('<tr><th>name</th><th>color</th></tr>').appendTo( $table );

// append a row for each fruit
for (var i in fruits) {
    // create a row, and set the background to the color of the fruit
    var $row = $('<tr/>', { css: { background: fruits[i].color } });

    // create a column and append to the row
    // we use text here so all HTML is escaped, to prevent hacking
    $('<td/>', { text: fruits[i].name }).appendTo( $row );

    // do the same for the color
    $('<td/>', { text: fruits[i].color }).appendTo( $row );

    // append the row to the table
    $row.appendTo( $table );
}

// all done, stick the table on the page
$table.appendTo('body');

Unfortunately, code like this usually ends up looking kludgy, and it's often hard to visualize what the final HTML will look like.

Templates let us turn the HTML/JavaScript relationship inside-out by putting the looping right in the HTML:

// define a template for the fruit table
// we'll use slashes at the end of each line to escape the line break
// this way we don't have to concatenate strings.
$.template('fruit-table', '\
    <table class="fruit-table"> \
        <tr><th>name</th><th>color</th></tr> \
        {{each rows}} \
            <tr style="background: ${color}"> \
                <td>${name}</td> \
                <td>${color}</td> \
            </tr> \
        {{/each}} \
    </table> \
');

// instantiate the template with the fruit array passed in as 'rows'
var $table = $.tmpl('fruit-table', { rows: fruits });

// that's it. stick it on the page.
$table.appendTo('body');

Now there's no question what the HTML will look like. It's in plain view.

If you'd like to jump on the chance to take the HTML out of your JavaScript completely, you can stick the same block on the page, in a special <script> block:

<script id="fruit-table" type="text/x-jquery-tmpl">

    <table class="fruit-table">
        <tr><th>name</th><th>color</th></tr>
        {{each rows}}
            <tr style="background: ${color}">
                <td>${name}</td>
                <td>${color}</td>
            </tr>
        {{/each}}
    </table>

</script>

Now we're down to a single line of code. Beautiful, isn't it?

$('#fruit-table').tmpl({ rows: fruits }).appendTo('body');

Now that we've gotten that taken care of, let's take it to the next level, and make a template that will dump any tabular data we give it:

<script id="table" type="text/x-jquery-tmpl">

{{if !data || data.length == 0 }}
    <p>No data.</p>
{{else}}
    <table class="${className}">
        <tr>
            {{each(key) data[0]}}
               <th>${key}</th>
            {{/each}}
        </tr>
        {{each(i, row) data}}
            <tr>
                {{each(key, value) row}}
                    <td>${value}</td>
                {{/each}}
            </tr>
        {{/each}}
    </table>
{{/if}}

</script>

$('#table').tmpl({
    data: fruits,
    className: 'fruits-table'
}).appendTo('body');

Want more? Check out the documentation and official announcements for lots more information:

• Templates documentation on jQuery API
• jQuery announcement
• Microsoft announcement