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Dijit Introduction

Authors:Peter Higgins, Bill Keese, Tobias Klipstein, Nikolai Onken, Craig Riecke,

Dijit is a widget system layered on top of Dojo. If you are new to the whole Dojo experience, Dijit is a good place to start. You can build amazing Web 2.0 GUI’s using very little, or no, JavaScript (though having an understanding of JavaScript will take you a long way, as will a good understanding of HTML and CSS).

Dijit Basics

You can use Dijit in one of two ways: declaratively by using special attributes inside of regular HTML tags, and programmatically through JavaScript (you are welcome to mix-and-match the two styles as you see fit). You have the same options either way.

dojo.require("dijit.Dialog");
dojo.ready(function(){
  // create a "hidden" Dialog:
  var dialog = new dijit.Dialog({ title:"Hello Dijit!" }, "someId");
  dialog.startup();

  // Hint: In order to open the dialog, you have to call
  // dialog.show();
});

is identical to:

<script type="text/javascript">
   dojo.require("dijit.Dialog");
</script>
<div data-dojo-type="dijit.Dialog" title="Hello Dijit!" id="someId"></div>

The declarative method requires you include the dojo.parser and have either dojoConfig.parseOnLoad set to true, or you manually call dojo.parser.parse() when you would like the widgets (aka: Dijits) to be created.

note: Dijit uses a special function for access, dijit.byId() ... This is not the same as dojo.byId, which works exclusively on DomNodes. Dijit stores all active widgets in the dijit.registry, and uses id’s as unique qualifiers. dijit.byId returns the instance (widget) from a passed ID, allowing you access to all the methods and properties within:

<script type="text/javascript">
   dojo.ready(function(){
       // dojo.byId("foobar") would only be a normal domNode.
       var myDialog = dijit.byId("foobar");
       myDialog.set("content", "<p>I've been replaced!</p>");
       myDialog.show();
   });
</script>
<div data-dojo-type="dijit.Dialog" id="foobar" title="Foo!">
   <p>I am some content</p>
</div>

If you need a reference to the actual Node used to display the widget, Dijit stores it as a property in the instance: .domNode. You can use this property for styling, positioning, or other DOM manipulation:

var thinger = dijit.byId("foobar");
dojo.place(thinger.domNode, dojo.body(), "last");
// functionally equivalent to:
// dojo.body().appendChild(thinger.domNode);

When creating widgets programmatically, pass an id:”” parameter:

var dialog = new dijit.Dialog({
   id:"myDialog",
   title:"Programmatic"
});
dialog.startup();
// compare them:
console.log(dijit.byId("myDialog") == dialog);

Otherwise, a unique ID will be generated for you:

var dialog = new dijit.Dialog({ title:"No ID" })
console.log(dialog.get("id"));

All Dijits follow the same programmatic convention. Create a new instance with the JavaScript new function, pass an object-hash of properties and functions (in this case, title:”No ID”), and supply an optional “source node reference”.

var node = dojo.byId("makeADialog");
var dialog = new dijit.Dialog({ title:"From Source Node" }, node);
dialog.show();

This will cause the creator to use the node with id=”makeADialog”, and turn it into a Dialog. You can pass a node reference directly (as seen above), or simply pass a string id. Either way, the reference passes through dojo.byId:

var dialog = new dijit.Dialog({ title:"From Source byId" }, "makeADialog");
dialog.show();

Attributes

Widgets have attributes much like DOM nodes. The attributes are one of the two main interfaces to programmatically interact with the widget. (The other interface is through event handlers like onClick().)

set() and get()

In general attributes can be both set at initialization and modified after the widget is created, although some attributes, like “id” and “type”, which are marked [const], can only be set at initialization. Other attributes, like “focused”, which are marked [readonly], can only be read.

This basically mirrors how vanilla HTML DOM nodes work, although the syntax is a bit different. Specifically, to get/set attributes after initialization, you need to use the get() and set() methods:

// set title
myTitlePane.set('title', 'hello world');

// find out if button is disabled
var dis = myButton.get('disabled');

// set to the current date
myDateTextBox.set('value', new Date());

Set() also supports a hash API like dojo.attr(), for setting multiple attributes:

myInput.set({ tabIndex: 3, disabled: true, value: 'hi'});

watch()

Attributes can also be monitored for changes. For example:

myTitlePane.watch("open", function(attr, oldVal, newVal){
   console.log("pane is now " + (newVal ? "opened" : "closed"));
});

Common Attributes of Dijits

There are several attributes common to (most) all Dijit instances. These appear as members to a widget instance, and can be accessed once you have a reference to the widget by one of the methods mentioned above. Some of the more popular are:

  • domNode - The top-level node in the widget. All widgets have a DOM Node attached to them, either through the srcNodeRef passed during instantiation, or a one created by the widget framework when declaring one programmatically. This is a real DOM Node, and is common in all Dijits. If you wish to show or hide a widget, for example, you would modify the CSS property display for the .domNode:
// hide a widget with id="myThiner"
dojo.style(dijit.byId("myThinger").domNode, "display", "none");
  • containerNode - If a widget uses a template to create complex markup and has inner markup to be displayed within the widget, the containerNode member is a reference to the node where the content was moved to. For example with a dijit.Dialog only the surrounding domNode is used to create the widget, and any contents of that node are set inside the template’s containerNode. When using set() to set and load content, this is the node that will be targeted for that content.
  • declaredClass - this is actually a relic of dojo.declare, which is how widgets are defined. The declaredClass is a string equal to the fully qualified name of the widget class.
var dialog = new dijit.Dialog({ title:"foo" }, "bar");
dialog.declaredClass == "dijit.Dialog" // true

Events

The other interface for dealing with widgets is to setup event handlers. For example:

new dijit.form.Button({
     label: 'Click me!',
     onClick: function(evt){ console.log("clicked!"); }
})

Event handlers can be setup programmatically (as above), or declaratively, like:

<div data-dojo-type="dijit.form.Button">
   <script type="dojo/connect" data-dojo-event="onClick" data-dojo-args="evt">
         console.log("clicked, event object is ", evt);
   </script>
   Click me!
</div>

Themes

Dijit comes bundled with four themes: Claro (Dojo 1.5+), Tundra, Soria, and Nihilo (all 1.0+). Themes are collections of images (icons and background images) and CSS, and bring a common visual style and color scheme to all the widgets. You can override the theme by container or by widget element to add nuance and flair.

To learn more about themes, see Dijit Themes and Theming.

Dijit i18n/a11y

Everything in Dijit is designed to be globally accessible – to accommodate users with different languages and cultures as well as those with different abilities. Language translations, bi-directional text, and cultural representation of things like numbers and dates are all encapsulated within the widgets. Server interactions are done in a way that makes no assumptions about local conventions. All widgets are keyboard accessible and using the standard Dijit theme, usable in high-contrast mode as well as by screen readers. These features are baked in so that, as much as possible, all users are treated equally.

Locating Widgets

There are many ways to locate a widget in a page, and access a reference to that widget. Widgets are Objects: collections of attributes and DomNode references. Once you have a reference to a widget, you can use that object (or any of its member properties) through that widget. There are three “main” ways to access a widget:

The simplest way to access a widget is dijit.byId. When the widget is created, if the Node used to create the widget (eg: srcNodeRef) had a DOM attribute id, that becomes the widget’s id in the dijit.registry.

With the following markup:

<div id="myDialog" data-dojo-type="dijit.Dialog" title="A Dialog"><p class="innerContent">Content</p>/div>

The Dialog instance would be available through the byId call to myDialog:

dijit.byId("myDialog").show(); // show my dialog instance

If the ID is unknown for some reason, the function dijit.getEnclosingWidget can be used by passing any child DOM Node reference. Again using the above markup, if we pass a reference to the p element inside the widget to getEnclosingWidget, we will again be returned a reference to the Dialog:

var node = dojo.query("p.innerContent")[0]; // a domNode found by query
var w = dijit.getEnclosingWidget(node); // find the widget this node is in
w.show();

The last, most common method, is a lot like getEnclosingWidget, though it only works if the node passed is the widget’s domNode member (aka: the top-level node in the template, or the node used to create the widget instance):

var w = dijit.byId("myDialog");
var node = w.domNode; // this is a bad example, but illustrates the relationship
var widget = dijit.byNode(node); // now, w == widget
widget.show();

Note: it typically doesn’t take that many lines to use dijit.byNode, this was a crafted example to illustrate the relationship between widgets and its domNode property. Most typically one would use byNode in some kind of event handler outside of the widget code:

dojo.connect(someNode, "onclick", function(e){
    var w = dijit.byNode(e.target);
    if(w){ w.show(); }
});

There are other ways of accessing and manipulating widgets, mostly involving the dijit.registry, a collection of all widgets active on a page.

Behavioral widgets

In general, widgets create their own DOM structure. For example,

var b = new dijit.form.Button({label: "press me"})

will create a new widget, where b.domNode can be inserted into the document at the appropriate point.

When instantiated declaratively,

<button data-dojo-type="dijit.form.Button">press me</button>

Note that the original button node is thrown away, after scanning the node for attribute settings and innerHTML. The new DOM automatically replaces the old button node.

However, there’s another type of widget called a “behavioral widget” that merely modifies the original node (called the srcNodeRef).

When using behavioral widgets, you need to specify a source DOM node for them to operate on. For example:

new dojox.widget.FishEyeLite({...}, "mySourceDom");

This comes naturally if you are instantiating from markup. For example, a behavioral widget to add a confirm dialog to an anchor might be used like this:

<a href="..." data-dojo-type="dojoc.widget.ConfirmAnchor">

Dijit doesn’t have any behavioral widgets, given that it’s meant to be able to be used in a purely programmatic setting (without requiring the developer to create any skeletal sourceDOM nodes), but it is a useful paradigm for some applications, and is supported by Dijit.