The goal of this blog entry is
to provide you with enough information
to start working with jQuery Templates. jQuery Templates enable you
to display and manipulate data
in the browser. For example, you can use jQuery Templates
to format and display a set of database records that you have retrieved with an Ajax call. jQuery Templates supports a number of powerful features such as template tags, template composition, and wrapped templates. I’ll concentrate on the features that I think that you will find most useful.
In order
to focus on the jQuery Templates feature itself, this blog entry is server technology agnostic. All the samples use HTML pages instead of
ASP.
NET pages.
In a future blog entry, I’ll focus on using jQuery Templates with
ASP.
NET Web Forms and
ASP.
NET MVC (You can do some pretty powerful things when jQuery Templates are used on the client and
ASP.
NET is used on the server). Introduction
to jQuery Templates The jQuery Templates plugin was developed by the Microsoft
ASP.
NET team
in collaboration with the open-source jQuery team. While working at Microsoft, I wrote the original proposal for jQuery Templates, Dave Reed wrote the original code, and Boris Moore wrote the final code. The jQuery team – especially John Resig – was very involved
in each step of the process. Both the jQuery community and
ASP.
NET communities were very active
in providing feedback. jQuery Templates will be included
in the jQuery core library (the jQuery.js library) when jQuery 1.5 is released. Until jQuery 1.5 is released, you can download the jQuery Templates plugin from the jQuery Source Code Repository or you can use jQuery Templates directly from the
ASP.
NET CDN. The documentation for jQuery Templates is already included with the official jQuery documentation at http://api.jQuery.com. The main entry for jQuery templates is located under the topic plugins/templates. A Basic Sample of jQuery Templates Let’s start with a really simple sample of using jQuery Templates. We’ll use the plugin
to display a list of books stored
in a JavaScript array. Here’s the complete code: <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html >
<head>
<title>Intro</title>
<link href="0_Site.css" rel="stylesheet" type="text/css" />
</head>
<body>
<div id="pageContent">
<h1>ASP.
NET Bookstore</h1>
<div id="bookContainer"></div>
</div>
<script id="bookTemplate" type="text/x-jQuery-tmpl">
<div>
<img src="BookPictures/${picture}" alt="" />
<h2>${title}</h2>
price: ${formatPrice(price)}
</div>
</script>
<script type="text/javascript" src="http://ajax.aspnetcdn.com/ajax/jQuery/jquery-1.4.4.js"></script>
<script type="text/javascript" src="http://ajax.aspnetcdn.com/ajax/jquery.templates/beta1/jquery.tmpl.js"></script>
<script type="text/javascript">
// Create an array of books
var books = [
{ title: "
ASP.
NET 4 Unleashed", price: 37.79, picture: "AspNet4Unleashed.jpg" },
{ title: "
ASP.
NET MVC Unleashed", price: 44.99, picture: "AspNetMvcUnleashed.jpg" },
{ title: "
ASP.
NET Kick Start", price: 4.00, picture: "AspNetKickStart.jpg" },
{ title: "
ASP.
NET MVC Unleashed iPhone", price: 44.99, picture: "AspNetMvcUnleashedIPhone.jpg" },
];
// Render the books using the template
$("#bookTemplate").tmpl(books).appendTo("#bookContainer");
function formatPrice(price) {
return "$" + price.toFixed(2);
}
</script>
</body>
</html>
When you open this page
in a browser, a list of books is displayed:
There are several things going on
in this page which require explanation.
First, notice that the page uses both the jQuery 1.4.4 and jQuery Templates libraries. Both libraries are retrieved from the
ASP.
NET CDN:
<script type="text/javascript" src="http://ajax.aspnetcdn.com/ajax/jQuery/jquery-1.4.4.js"></script>
<script type="text/javascript" src="http://ajax.aspnetcdn.com/ajax/jquery.templates/beta1/jquery.tmpl.js"></script>
You can use the
ASP.
NET CDN for free (even for production websites). You can learn more about the files included on the
ASP.
NET CDN by visiting the
ASP.
NET CDN documentation page.
Second, you should notice that the actual template is included
in a script tag with a special MIME type:
<script id="bookTemplate" type="text/x-jQuery-tmpl">
<div>
<img src="BookPictures/${picture}" alt="" />
<h2>${title}</h2>
price: ${formatPrice(price)}
</div>
</script>
This template is displayed for each of the books rendered by the template. The template displays a book picture, title, and price.
Notice that the SCRIPT tag which wraps the template has a MIME type of text/x-jQuery-tmpl. Why is the template wrapped
in a SCRIPT tag and why the strange MIME type?
When a browser encounters a SCRIPT tag with an unknown MIME type, it ignores the content of the tag. This is the behavior that you want with a template. You don’t want a browser
to attempt
to parse the contents of a template because this might cause side effects.
For example, the template above includes an <img> tag with a src attribute that points at “BookPictures/${picture}”. You don’t want the browser
to attempt
to load an
image at the URL “BookPictures/${picture}”. Instead, you want
to prevent the browser from processing the IMG tag until the ${picture} expression is replaced by with the actual name of an
image by the jQuery Templates plugin.
If you are not worried about browser side-effects then you can wrap a template inside any HTML tag that you please. For example, the following DIV tag would also work with the jQuery Templates plugin:
<div id="bookTemplate" style="display:none">
<div>
<h2>${title}</h2>
price: ${formatPrice(price)}
</div>
</div>
Notice that the DIV tag includes a style=”display:none” attribute
to prevent the template from being displayed until the template is parsed by the jQuery Templates plugin.
Third, notice that the expression ${…} is used
to display the value of a JavaScript expression within a template. For example, the expression ${title} is used
to display the value of the book title property. You can use any JavaScript function that you please within the ${…} expression. For example,
in the template above, the book price is formatted with the help of the custom JavaScript formatPrice() function which is defined lower
in the page.
Fourth, and finally, the template is rendered with the help of the tmpl() method. The following statement selects the bookTemplate and renders an array of books using the bookTemplate. The results are appended
to a DIV element named bookContainer by using the standard jQuery appendTo() method.
$("#bookTemplate").tmpl(books).appendTo("#bookContainer");
Using Template Tags
Within a template, you can use any of the following template tags.
{{tmpl}} – Used for template composition. See the section below.
{{wrap}} – Used for wrapped templates. See the section below.
{{each}} – Used
to iterate through a collection.
{{if}} – Used
to conditionally display template content.
{{else}} – Used with {{if}}
to conditionally display template content.
{{html}} – Used
to display the value of an HTML expression without encoding the value. Using ${…} or {{= }} performs HTML encoding automatically.
{{= }}-- Used
in exactly the same way as ${…}.
{{! }} – Used for displaying comments. The contents of a {{!...}} tag are ignored.
For example, imagine that you want
to display a list of blog entries. Each blog entry could, possibly, have an associated list of categories. The following page illustrates
how you can use the { if}} and {{each}} template tags
to conditionally display categories for each blog entry:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title>each</title>
<link href="1_Site.css" rel="stylesheet" type="text/css" />
</head>
<body>
<div id="blogPostContainer"></div>
<script id="blogPostTemplate" type="text/x-jQuery-tmpl">
<h1>${postTitle}</h1>
<p>
${postEntry}
</p>
{{if categories}}
Categories: {{each categories}} <i>${$value}</i> {{/each}}
{{else}}
Uncategorized
{{/if}}
</script>
<script type="text/javascript" src="http://ajax.aspnetcdn.com/ajax/jQuery/jquery-1.4.4.js"></script>
<script type="text/javascript" src="http://ajax.aspnetcdn.com/ajax/jquery.templates/beta1/jquery.tmpl.js"></script>
<script type="text/javascript">
var blogPosts = [
{
postTitle: "
How to fix a sink plunger
in 5 minutes",
postEntry: "Lorem ipsum dolor sit amet, consectetuer adipiscing elit. Maecenas porttitor congue massa. Fusce posuere, magna sed pulvinar ultricies, purus lectus malesuada libero, sit amet commodo magna eros quis urna.",
categories: ["HowTo", "Sinks", "Plumbing"]
},
{
postTitle: "
How to remove a broken lightbulb",
postEntry: "Lorem ipsum dolor sit amet, consectetuer adipiscing elit. Maecenas porttitor congue massa. Fusce posuere, magna sed pulvinar ultricies, purus lectus malesuada libero, sit amet commodo magna eros quis urna.",
categories: ["HowTo", "Lightbulbs", "Electricity"]
},
{
postTitle: "New associate website",
postEntry: "Lorem ipsum dolor sit amet, consectetuer adipiscing elit. Maecenas porttitor congue massa. Fusce posuere, magna sed pulvinar ultricies, purus lectus malesuada libero, sit amet commodo magna eros quis urna."
}
];
// Render the blog posts
$("#blogPostTemplate").tmpl(blogPosts).appendTo("#blogPostContainer");
</script>
</body>
</html>
When this page is opened
in a
web browser, the following list of blog posts and categories is displayed:
Notice that the first and second blog entries have associated categories but the third blog entry does not. The third blog entry is “Uncategorized”.
The template used
to render the blog entries and categories looks like this:
<script id="blogPostTemplate" type="text/x-jQuery-tmpl">
<h1>${postTitle}</h1>
<p>
${postEntry}
</p>
{{if categories}}
Categories: {{each categories}} <i>${$value}</i> {{/each}}
{{else}}
Uncategorized
{{/if}}
</script>
Notice the special expression $value used within the {{each}} template tag. You can use $value
to display the value of the current template item.
In this case, $value is used
to display the value of each category
in the collection of categories.
Template Composition
When building a fancy page, you might want
to build a template out of multiple templates.
In other words, you might want
to take advantage of template composition.
For example, imagine that you want
to display a list of products. Some of the products are being sold at their normal price and some of the products are on sale.
In that case, you might want
to use two different templates for displaying a product: a productTemplate and a productOnSaleTemplate.
The following page illustrates
how you can use the {{tmpl}} tag
to build a template from multiple templates:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title>Composition</title>
<link href="2_Site.css" rel="stylesheet" type="text/css" />
</head>
<body>
<div id="pageContainer">
<h1>Products</h1>
<div id="productListContainer"></div>
<!-- Show list of products using composition -->
<script id="productListTemplate" type="text/x-jQuery-tmpl">
<div>
{{if onSale}}
{{tmpl "#productOnSaleTemplate"}}
{{else}}
{{tmpl "#productTemplate"}}
{{/if}}
</div>
</script>
<!-- Show product -->
<script id="productTemplate" type="text/x-jQuery-tmpl">
${name}
</script>
<!-- Show product on sale -->
<script id="productOnSaleTemplate" type="text/x-jQuery-tmpl">
<b>${name}</b> <img src="images/on_sale.png" alt="On Sale" />
</script>
<script type="text/javascript" src="http://ajax.aspnetcdn.com/ajax/jQuery/jquery-1.4.4.js"></script>
<script type="text/javascript" src="http://ajax.aspnetcdn.com/ajax/jquery.templates/beta1/jquery.tmpl.js"></script>
<script type="text/javascript">
var products = [
{ name: "Laptop", onSale: false },
{ name: "Apples", onSale: true },
{ name: "Comb", onSale: false }
];
$("#productListTemplate").tmpl(products).appendTo("#productListContainer");
</script>
</div>
</body>
</html>
In the page above, the main template used
to display the list of products looks like this:
<script id="productListTemplate" type="text/x-jQuery-tmpl">
<div>
{{if onSale}}
{{tmpl "#productOnSaleTemplate"}}
{{else}}
{{tmpl "#productTemplate"}}
{{/if}}
</div>
</script>
If a product is on sale then the product is displayed with the productOnSaleTemplate (which includes an on sale image):
<script id="productOnSaleTemplate" type="text/x-jQuery-tmpl">
<b>${name}</b> <img src="images/on_sale.png" alt="On Sale" />
</script>
Otherwise, the product is displayed with the normal productTemplate (which does not include the on sale image):
<script id="productTemplate" type="text/x-jQuery-tmpl">
${name}
</script>
You can pass a parameter
to the {{tmpl}} tag. The parameter becomes the data passed
to the template rendered by the {{tmpl}} tag.
For example,
in the previous section, we used the {{each}} template tag
to display a list of categories for each blog entry like this:
<script id="blogPostTemplate" type="text/x-jQuery-tmpl">
<h1>${postTitle}</h1>
<p>
${postEntry}
</p>
{{if categories}}
Categories: {{each categories}} <i>${$value}</i> {{/each}}
{{else}}
Uncategorized
{{/if}}
</script>
Another way
to create this template is
to use template composition like this:
<script id="blogPostTemplate" type="text/x-jQuery-tmpl">
<h1>${postTitle}</h1>
<p>
${postEntry}
</p>
{{if categories}}
Categories: {{tmpl(categories) "#categoryTemplate"}}
{{else}}
Uncategorized
{{/if}}
</script>
<script id="categoryTemplate" type="text/x-jQuery-tmpl">
<i>${$data}</i>
</script>
Using the {{each}} tag or {{tmpl}} tag is largely a matter of personal preference.
Wrapped Templates
The {{wrap}} template tag enables you
to take a chunk of HTML and transform the HTML into another chunk of HTML (think easy XSLT). When you use the {{wrap}} tag, you work with two templates. The first template contains the HTML being transformed and the second template includes the filter expressions for transforming the HTML.
For example, you can use the {{wrap}} template tag
to transform a chunk of HTML into an interactive tab strip:
When you click any of the tabs, you see the corresponding content.
This tab strip was created with the following page:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title>Wrapped Templates</title>
<style type="text/css">
body {
font-family: Arial;
background-color:black;
}
.tabs div {
display:inline-block;
border-bottom: 1px solid black;
padding:4px;
background-color:gray;
cursor:pointer;
}
.tabs div.tabState_true {
background-color:white;
border-bottom:1px solid white;
}
.tabBody {
border-top:1px solid white;
padding:10px;
background-color:white;
min-height:400px;
width:400px;
}
</style>
</head>
<body>
<div id="tabsView"></div>
<script id="tabsContent" type="text/x-jquery-tmpl">
{{wrap "#tabsWrap"}}
<h3>Tab 1</h3>
<div>
Content of tab 1.
Lorem ipsum dolor <b>sit</b> amet, consectetuer adipiscing elit. Maecenas porttitor congue massa. Fusce posuere, magna sed pulvinar ultricies, purus lectus malesuada libero, sit amet commodo magna eros quis urna.
</div>
<h3>Tab 2</h3>
<div>
Content of tab 2.
Lorem ipsum dolor <b>sit</b> amet, consectetuer adipiscing elit. Maecenas porttitor congue massa. Fusce posuere, magna sed pulvinar ultricies, purus lectus malesuada libero, sit amet commodo magna eros quis urna.
</div>
<h3>Tab 3</h3>
<div>
Content of tab 3.
Lorem ipsum dolor <b>sit</b> amet, consectetuer adipiscing elit. Maecenas porttitor congue massa. Fusce posuere, magna sed pulvinar ultricies, purus lectus malesuada libero, sit amet commodo magna eros quis urna.
</div>
{{/wrap}}
</script>
<script id="tabsWrap" type="text/x-jquery-tmpl">
<div class="tabs">
{{each $item.html("h3", true)}}
<div class="tabState_${$index === selectedTabIndex}">
${$value}
</div>
{{/each}}
</div>
<div class="tabBody">
{{html $item.html("div")[selectedTabIndex]}}
</div>
</script>
<script type="text/javascript" src="http://ajax.aspnetcdn.com/ajax/jQuery/jquery-1.4.4.js"></script>
<script type="text/javascript" src="http://ajax.aspnetcdn.com/ajax/jquery.templates/beta1/jquery.tmpl.js"></script>
<script type="text/javascript">
// Global for tracking selected tab
var selectedTabIndex = 0;
// Render the tab strip
$("#tabsContent").tmpl().appendTo("#tabsView");
// When a tab is clicked, update the tab strip
$("#tabsView")
.delegate(".tabState_false", "click", function () {
var templateItem = $.tmplItem(this);
selectedTabIndex = $(this).index();
templateItem.update();
});
</script>
</body>
</html>
The “source” for the tab strip is contained
in the following template:
<script id="tabsContent" type="text/x-jquery-tmpl">
{{wrap "#tabsWrap"}}
<h3>Tab 1</h3>
<div>
Content of tab 1.
Lorem ipsum dolor <b>sit</b> amet, consectetuer adipiscing elit. Maecenas porttitor congue massa. Fusce posuere, magna sed pulvinar ultricies, purus lectus malesuada libero, sit amet commodo magna eros quis urna.
</div>
<h3>Tab 2</h3>
<div>
Content of tab 2.
Lorem ipsum dolor <b>sit</b> amet, consectetuer adipiscing elit. Maecenas porttitor congue massa. Fusce posuere, magna sed pulvinar ultricies, purus lectus malesuada libero, sit amet commodo magna eros quis urna.
</div>
<h3>Tab 3</h3>
<div>
Content of tab 3.
Lorem ipsum dolor <b>sit</b> amet, consectetuer adipiscing elit. Maecenas porttitor congue massa. Fusce posuere, magna sed pulvinar ultricies, purus lectus malesuada libero, sit amet commodo magna eros quis urna.
</div>
{{/wrap}}
</script>
The tab strip is created with a list of H3 elements (which represent each tab) and DIV elements (which represent the body of each tab). Notice that the HTML content is wrapped
in the {{wrap}} template tag. This template tag points at the following tabsWrap template:
<script id="tabsWrap" type="text/x-jquery-tmpl">
<div class="tabs">
{{each $item.html("h3", true)}}
<div class="tabState_${$index === selectedTabIndex}">
${$value}
</div>
{{/each}}
</div>
<div class="tabBody">
{{html $item.html("div")[selectedTabIndex]}}
</div>
</script>
The tabs DIV contains all of the tabs. The {{each}} template tag is used
to loop through each of the H3 elements from the source template and render a DIV tag that represents a particular tab.
The template item html() method is used
to filter content from the “source” HTML template. The html() method accepts a jQuery selector for its first parameter. The tabs are retrieved from the source template by using an h3 filter.
The second parameter passed
to the html() method – the textOnly parameter -- causes the filter
to return the inner text of each h3 element. You can learn more about the html() method at the jQuery website (see the section on $item.html()).
The tabBody DIV renders the body of the selected tab. Notice that the {{html}} template tag is used
to display the tab body so that HTML content
in the body won’t be HTML encoded.
The html() method is used, once again,
to grab all of the DIV elements from the source HTML template. The selectedTabIndex global variable is used
to display the contents of the selected tab.
Remote Templates
A common feature request for jQuery templates is support for remote templates. Developers want
to be able
to separate templates into different files.
Adding support for remote templates requires only a few lines of extra code (Dave Ward has a nice blog entry on this). For example, the following page uses a remote template from a file named BookTemplate.htm:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title>Remote Templates</title>
<link href="0_Site.css" rel="stylesheet" type="text/css" />
</head>
<body>
<div id="pageContent">
<h1>ASP.
NET Bookstore</h1>
<div id="bookContainer"></div>
</div>
<script type="text/javascript" src="http://ajax.aspnetcdn.com/ajax/jQuery/jquery-1.4.4.js"></script>
<script type="text/javascript" src="http://ajax.aspnetcdn.com/ajax/jquery.templates/beta1/jquery.tmpl.js"></script>
<script type="text/javascript">
// Create an array of books
var books = [
{ title: "
ASP.
NET 4 Unleashed", price: 37.79, picture: "AspNet4Unleashed.jpg" },
{ title: "
ASP.
NET MVC Unleashed", price: 44.99, picture: "AspNetMvcUnleashed.jpg" },
{ title: "
ASP.
NET Kick Start", price: 4.00, picture: "AspNetKickStart.jpg" },
{ title: "
ASP.
NET MVC Unleashed iPhone", price: 44.99, picture: "AspNetMvcUnleashedIPhone.jpg" },
];
//
Get the remote template
$.get("BookTemplate.htm", null, function (bookTemplate) {
// Render the books using the remote template
$.tmpl(bookTemplate, books).appendTo("#bookContainer");
});
function formatPrice(price) {
return "$" + price.toFixed(2);
}
</script>
</body>
</html>
The remote template is retrieved (and rendered) with the following code:
//
Get the remote template
$.get("BookTemplate.htm", null, function (bookTemplate) {
// Render the books using the remote template
$.tmpl(bookTemplate, books).appendTo("#bookContainer");
});
This code uses the standard jQuery $.get() method
to get the BookTemplate.htm file from the server with an Ajax request. After the BookTemplate.htm file is successfully retrieved, the $.tmpl() method is used
to render an array of books with the template. Here’s what the BookTemplate.htm file looks like:
<div>
<img src="BookPictures/${picture}" alt="" />
<h2>${title}</h2>
price: ${formatPrice(price)}
</div>
Notice that the template
in the BooksTemplate.htm file is not wrapped by a SCRIPT element. There is no need
to wrap the template
in this case because there is no possibility that the template will
get interpreted before you want it
to be interpreted.
If you plan
to use the bookTemplate multiple times – for example, you are paging or sorting the books -- then you should compile the template into a function and cache the compiled template function.
For example, the following page can be used
to page through a list of 100 products (using iPhone style More paging).
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title>Template Caching</title>
<link href="6_Site.css" rel="stylesheet" type="text/css" />
</head>
<body>
<h1>Products</h1>
<div id="productContainer"></div>
<button id="more">More</button>
<script type="text/javascript" src="http://ajax.aspnetcdn.com/ajax/jQuery/jquery-1.4.4.js"></script>
<script type="text/javascript" src="http://ajax.aspnetcdn.com/ajax/jquery.templates/beta1/jquery.tmpl.js"></script>
<script type="text/javascript">
// Globals
var pageIndex = 0;
// Create an array of products
var products = [];
for (var i = 0; i < 100; i++) {
products.push({ name: "Product " + (i + 1) });
}
//
Get the remote template
$.get("ProductTemplate.htm", null, function (productTemplate) {
// Compile and cache the template
$.template("productTemplate", productTemplate);
// Render the products
renderProducts(0);
});
$("#more").click(function () {
pageIndex++;
renderProducts();
});
function renderProducts() {
//
Get page of products
var pageOfProducts = products.slice(pageIndex * 5, pageIndex * 5 + 5);
// Used cached productTemplate
to render products
$.tmpl("productTemplate", pageOfProducts).appendTo("#productContainer");
}
function formatPrice(price) {
return "$" + price.toFixed(2);
}
</script>
</body>
</html>
The ProductTemplate is retrieved from an external file named ProductTemplate.htm. This template is retrieved only once. Furthermore, it is compiled and cached with the help of the $.template() method:
//
Get the remote template
$.get("ProductTemplate.htm", null, function (productTemplate) {
// Compile and cache the template
$.template("productTemplate", productTemplate);
// Render the products
renderProducts(0);
});
The $.template() method compiles the HTML representation of the template into a JavaScript function and caches the template function with the name productTemplate.
The cached template can be used by calling the $.tmp() method. The productTemplate is used
in the renderProducts() method:
function renderProducts() {
//
Get page of products
var pageOfProducts = products.slice(pageIndex * 5, pageIndex * 5 + 5);
// Used cached productTemplate
to render products
$.tmpl("productTemplate", pageOfProducts).appendTo("#productContainer");
}
In the code above, the first parameter passed
to the $.tmpl() method is the name of a cached template.
Working with Template Items
In this final section, I want
to devote some space
to discussing Template Items. A new Template Item is created for each rendered instance of a template. For example, if you are displaying a list of 100 products with a template, then 100 Template Items are created.
A Template Item has the following properties and methods:
data – The data associated with the Template Instance. For example, a product.
tmpl – The template associated with the Template Instance.
parent – The parent template item if the template is nested.
nodes – The HTML content of the template.
calls – Used by {{wrap}} template tag.
nest – Used by {{tmpl}} template tag.
wrap – Used
to imperatively enable wrapped templates.
html – Used
to filter content from a wrapped template. See the above section on wrapped templates.
update – Used
to re-render a template item.
The last method – the update() method -- is especially interesting because it enables you
to re-render a template item with new data or even a new template.
For example, the following page displays a list of books. When you hover your mouse over any of the books, additional book details are displayed.
In the following screenshot, details for
ASP.
NET Kick Start are displayed.
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title>Template Item</title>
<link href="0_Site.css" rel="stylesheet" type="text/css" />
</head>
<body>
<div id="pageContent">
<h1>ASP.
NET Bookstore</h1>
<div id="bookContainer"></div>
</div>
<script id="bookTemplate" type="text/x-jQuery-tmpl">
<div class="bookItem">
<img src="BookPictures/${picture}" alt="" />
<h2>${title}</h2>
price: ${formatPrice(price)}
</div>
</script>
<script id="bookDetailsTemplate" type="text/x-jQuery-tmpl">
<div class="bookItem">
<img src="BookPictures/${picture}" alt="" />
<h2>${title}</h2>
price: ${formatPrice(price)}
<p>
${description}
</p>
</div>
</script>
<script type="text/javascript" src="http://ajax.aspnetcdn.com/ajax/jQuery/jquery-1.4.4.js"></script>
<script type="text/javascript" src="http://ajax.aspnetcdn.com/ajax/jquery.templates/beta1/jquery.tmpl.js"></script>
<script type="text/javascript">
// Create an array of books
var books = [
{ title: "
ASP.
NET 4 Unleashed", price: 37.79, picture: "AspNet4Unleashed.jpg", description: "The most comprehensive book on Microsoft’s new
ASP.
NET 4.. " },
{ title: "
ASP.
NET MVC Unleashed", price: 44.99, picture: "AspNetMvcUnleashed.jpg", description: "Writing for professional programmers, Walther explains the crucial concepts that make the Model-View-Controller (MVC) development paradigm work…" },
{ title: "
ASP.
NET Kick Start", price: 4.00, picture: "AspNetKickStart.jpg", description: "Visual Studio .
NET is the premier development environment for creating .
NET applications…." },
{ title: "
ASP.
NET MVC Unleashed iPhone", price: 44.99, picture: "AspNetMvcUnleashedIPhone.jpg", description: "
ASP.
NET MVC Unleashed for the iPhone…" },
];
// Render the books using the template
$("#bookTemplate").tmpl(books).appendTo("#bookContainer");
//
Get compiled details template
var bookDetailsTemplate = $("#bookDetailsTemplate").template();
// Add hover handler
$(".bookItem").mouseenter(function () {
//
Get template item associated with DIV
var templateItem = $(this).tmplItem();
// Change template
to compiled template
templateItem.tmpl = bookDetailsTemplate;
// Re-render template
templateItem.update();
});
function formatPrice(price) {
return "$" + price.toFixed(2);
}
</script>
</body>
</html>
There are two templates used
to display a book: bookTemplate and bookDetailsTemplate. When you hover your mouse over a template item, the standard bookTemplate is swapped out for the bookDetailsTemplate. The bookDetailsTemplate displays a book description.
The books are rendered with the bookTemplate with the following line of code:
// Render the books using the template
$("#bookTemplate").tmpl(books).appendTo("#bookContainer");
The following code is used
to swap the bookTemplate and the bookDetailsTemplate
to show details for a book:
//
Get compiled details template
var bookDetailsTemplate = $("#bookDetailsTemplate").template();
// Add hover handler
$(".bookItem").mouseenter(function () {
//
Get template item associated with DIV
var templateItem = $(this).tmplItem();
// Change template
to compiled template
templateItem.tmpl = bookDetailsTemplate;
// Re-render template
templateItem.update();
});
When you hover your mouse over a DIV element rendered by the bookTemplate, the mouseenter handler executes. First, this handler retrieves the Template Item associated with the DIV element by calling the tmplItem() method. The tmplItem() method returns a Template Item.
Next, a new template is assigned
to the Template Item. Notice that a compiled version of the bookDetailsTemplate is assigned
to the Template Item’s tmpl property. The template is compiled earlier
in the code by calling the template() method.
Finally, the Template Item update() method is called
to re-render the Template Item with the bookDetailsTemplate instead of the original bookTemplate.
Summary
This is a long blog entry and I still have not managed
to cover all of the features of jQuery Templates J However, I’ve tried
to cover the most important features of jQuery Templates such as template composition, template wrapping, and template items.
To learn more about jQuery Templates, I recommend that you look at the documentation for jQuery Templates at the official jQuery website. Another great way
to learn more about jQuery Templates is
to look at the (unminified) source code.
