Dojo Toolkit (stylized as dōjō toolkit) is an open-source modular JavaScript library (or more specifically JavaScript toolkit) designed to ease the rapid development of cross-platform, JavaScript/Ajax-based applications and web sites. It was started by Alex Russell, Dylan Schiemann, David Schontzler, and others in 2004 and is dual-licensed under the modified BSD license or the Academic Free License (≥ 2.1).
The Dojo Foundation was a non-profit organization created with the goal to promote the adoption of the toolkit. In 2016, the foundation merged with jQuery Foundation to become JS Foundation.
Overview
Dojo is a JavaScript framework targeting the many needs of large-scale client-side web development. For example, Dojo abstracts the differences among diverse browsers to provide APIs that will work on all of them (it can even run on the server under Node.js); it establishes a framework for defining modules of code and managing their interdependencies; it provides build tools for optimizing JavaScript and CSS, generating documentation, and unit testing; it supports internationalization, localization, and accessibility; and it provides a rich suite of commonly needed utility classes and user-interface widgets.
Dojo is completely open source. The toolkit includes about three thousand JavaScript modules, in addition to images and other resources.
The Dojo Toolkit is organized in several parts: dojo contains the core and most non-visual modules. dijit is a library of user-interface modules for widgets and layout. dojox holds assorted modules not yet considered stable enough to include in dojo or dijit. util includes build tools such as optimization, documentation, style-checking, and testing.
Features
Widgets
Dojo widgets are components — comprising JavaScript code, HTML markup, and CSS style declarations — that provide multi-browser (not to be confused with cross-browser), interactive features:
Menus, tabs, and tooltips
Sortable tables
Dynamic charts
2D vector drawings
Animated effects—fades, wipes and slides—facilities for custom animation effects
Asynchronous communication
One important feature of Ajax applications is asynchronous communication of the browser with the server: information is exchanged and the page's presentation is updated without a need for reloading the whole page. Traditionally, this is done with the JavaScript object XMLHttpRequest. Dojo provides an abstracted wrapper (dojo.xhr) around various web browsers' implementations of XMLHttpRequest, and dojo.io also supports other transports (such as hidden IFrames) and a variety of data formats. Using this approach, it is easy to have the data a user enters into a form sent to the server "behind the scenes"; the server can then reply with some JavaScript code that updates the presentation of the page.
Packaging system
Dojo provides a packaging system to facilitate modular development of functionality in individual packages and sub-packages; the base Dojo "bootstrap" script initializes a set of hierarchical package namespaces — "io", "event", etc. — under a root "dojo" namespace. After initialization of the root namespace, any Dojo package can be loaded (via XMLHttpRequest or other similar transport) by using utility functions supplied in the bootstrap. It is also possible to initialize additional namespaces within or parallel to the "dojo" namespace, allowing extensions of Dojo or the development of private Dojo-managed namespaces for third-party libraries and applications.
Dojo packages can consist of multiple files and can specify which files constitute the entire package. Any package or file can also specify a dependency on other packages or files; when the package is loaded, any dependencies it specifies will also be loaded.
Workarounds for cross-domain loading of most Dojo packages are provided (though this requires a specialized build of Dojo).
Dojo also provides a mechanism for building "profiles"; the build system takes as input a list of packages, and uses Rhino to create a single compressed JavaScript file containing those packages and all their dependencies. This allows all necessary code to be loaded and initialized at once, and permits caching of the code (most web browsers do not cache files loaded via XMLHttpRequest). Pre-built profiles for some common use cases are available for download from the same location as the full toolkit.