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    system/events

    Unstable

    API for working with the application observer service.

    Usage

    The system/events module provides core (low level) API for working with the application observer service, also known as nsIObserverService. You can find a list of events dispatched by firefox codebase here.

    var events = require("sdk/system/events");
    var { Ci } = require("chrome");
    
    function listener(event) {
      var channel = event.subject.QueryInterface(Ci.nsIHttpChannel);
      channel.setRequestHeader("User-Agent", "MyBrowser/1.0", false);
    }
    
    events.on("http-on-modify-request", listener);
    

    Globals

    Functions

    emit(type, event)

    Send an event to observer service

    Parameters

    type : string
    The event type.

    event : object
    An optional object object with data and subject attributes. data refers to a string that you would like to pass through this event. subject should refer to the actual actor/subject of this event (ie: the object emitting the event).

    on(type, listener, strong)

    Listen to events of a given type

    Parameters

    type : string
    The event type name to watch.

    listener : function
    Function that will be called when an event is fired, with a single event object as argument. This object has three attributes:

    • type: the event type name
    • subject: the event subject object
    • data: the event data string

    strong : boolean
    Default is false, a weak reference, which means it can be garbage collected at any time if there are no other references to it. Determines if we should keep a strong or weak reference to the listener method.

    once(type, listener, strong)

    Listen only once to a particular event type

    Parameters

    type : string
    The event type name to watch.

    listener : function
    Function that will be called when an event is fired.

    strong : boolean
    Default is false, a weak reference, which means it can be garbage collected at any time if there are no other references to it. Determines if we should keep a strong or weak reference to the listener method.

    off(type, listener)

    Stop listening for an event

    Parameters

    type : string
    The event type name to unsubscribe to.

    listener : function
    The function we registered to listen for events.

    Document Tags and Contributors

    Contributors to this page: wbamberg, jsantell, grbradt, Hub
    Last updated by: grbradt,
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