api-idioms.md

Common Idioms

Constructors

Many SDK modules export constructors that create object instances for use by add-on code.

A constructor takes a single argument, an object typically referred to as options and supplied as an object literal listing values for named object properties. So you will generally see objects constructed using the following pattern:

var sdkModule = require("sdk-module");

var mySdkObject = sdkModule.sdkObject({
  property1: value1,
  property2: value2
});

Events

The SDK supports event-driven programming: objects which are event emitters can emit events such as pages loading, windows opening and user interactions.

Add-on developers can register listeners with event emitters and are then notified when the events occur.

To learn more about events, see the Working with Events page.

Content Scripting

Several modules need to interact directly with web content, either web content they host themselves (such as the panel module) or web content hosted by the browser (such as the page-mod).

These modules follow a common pattern in which the code that actually interacts with the content is executed as a separate script called a content script. The content script and the main add-on script communicate using an asynchronous message-passing mechanism.

Objects that implement this scheme include properties that specify which content scripts should be run and when.

To learn more about content scripts, see the Working with Content Scripts page.

**Next**: [module overview](dev-guide/addon-development/api-modules.html).