Dojo has long provided support for declaring widgets and specifying other information directly in HTML. This support makes it extremely quick and easy to get an application started. You can start instantiating widgets by adding attributes to HTML elements before even writing any code. This is not only a very convenient tool, but using a declarative approach to binding widgets to elements can be viewed as cleaner and more organized than using the imperative mechanics of JavaScript. Widgets declared in markup have an encapsulated construction, avoiding instantiation that requires spanning and synchronizing HTML and code manually.

However, the use of Dojo’s declarative tools has been avoided by some because it uses custom attributes that are outside the HTML specification. While this approach works in every browser on the market and is implicitly allowed, it does not validate against the HTML4 validators. Now, the new HTML5 specification provides a namespace for custom attributes. The data-* attributes are available for libraries and authors to use for their own purposes and extensions while still having validating markup. The HTML5 specification further recommends that library use a sub-namespace for their custom attributes to avoid conflicts with other code. All of the Dojo custom attributes begin with data-dojo-. Let’s look at the new Dojo attributes.

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