Difference between registry.byId and dom.byId in dojo? What is the advantage of using registry.byId?

Question

What is the difference between registry.byId and dom.byId in dojo? What is the advantage of using registry.byId?

In the code below I'm using dijit/registry and dojo/dom for both my textbox (#myTextBox3) and my textbox node (#textNode3). Only two of them are providing results.

require(["dojo/parser", "dojo/dom", "dijit/registry", "dijit/form/TextBox", "dojo/domReady!"],
    function(parser, dom, registry) {

    parser.parse();

    // Locate the JS object.
    var dibiWidget = registry.byId("myTextBox3");
    var dobiWidget = dom.byId("myTextBox3");
    var dibiDOM = registry.byId("textNode3");
    var dobiDOM = dom.byId("textNode3");


    dom.byId("textNode3").innerHTML = "registry.byId for widget id returned: " + dibiWidget + "<br>" +
        "dom.byId for widget id returned: " + dobiWidget + "<br>" +
        "registry.byId for dom id returned: " + dibiDOM + "<br>" +
        "dom.byId for dom id returned: " + dobiDOM + "<br>";
});

Answer 1

These modules have a different usage. So there is no advantage of using registry.byId() (or dom.byId()) because they differ in use case.

dijit/registry::byId()

The dijit/registry module main use is retrieving widget instances. Quoting the reference guide:

dijit/registry stores a collection of all the dijit widgets within a page. It is commonly used to retrieve a reference to a widget from a related piece of data

dojo/dom::byId()

The dojo/dom module on the other hand is just a module to access DOM nodes. Quoting the information of byId() on the reference guide:

This is a simple alias to document.getElementById, which not only is shorter to write, but fortunately works in all browsers. It turns a domNode reference to some Node byId, or the same node reference if passed a domNode.

What does it mean?

The registry.byId() function will return an instance of your widget. This contains setters/getters and other stuff from the widget. This module should only be used to retrieve widgets, you cannot get a DOM node with it.

The dom.byId() function on the other hand will return the matching DOM node. You can only use it to retrieve a DOM node. A widget obviously also contains DOM nodes, but you should never directly access the DOM nodes of a widget because they're part of the internal structure of the widget (and may change).

When accessing a widget, always use registry.byId(). It provides APIs to access most DOM properties anyways.

---

Your code

So, your code demonstrates the 4 possibilities here. Assuming #myTextBox3 is a widget (for example of type dijit/form/TextBox) and #textNode3 is a DOM node, the following will happen:

• dibiWidget will work because #myTextBox3 is a widget. It will return a reference to that widget
• dobiWidget will probably work, because there is a DOM node behind every widget with the same ID (not required though). However, like I just explained, it's not recommended to use it.
• dibiDom will not work because there is no widget with ID #textNode3. This is just a simple DOM node.
• dobiDom will return a reference to the DOM node and will work.

I also made a small JSFiddle to demonstrate this.

Answer 2

dom.byId() is just short for document.getElementById(...). It returns a reference to the dom node.

registry.byId(...) returns a reference to a dojo widget that is contained in dojo's registry.

For example if you have <div id='myDiv'></div>, You can't call registry.byId('myDiv') here because it isn't a dojo widget (thus isn't in the dojo registry). You can call dom.byId('myDiv').

Now if you had <div id='myDiv' data-dojo-type='dijit/layout/ContentPane'></div>, You can call both dom.byId('myDiv') and registry.byId('myDiv'). One gets you the dom node and the other gets you the dojo widget. Both will have different methods available to them but I generally favor registry.byId(...) if there is an overlap.

There isn't an advantage to using one or the other because they are both different things and used for different things.

https://dojotoolkit.org/reference-guide/1.9/dijit/registry.html

http://dojotoolkit.org/reference-guide/1.9/dojo/dom.html