events.md

ZJS API for Events

• Introduction
• Web IDL
• Class: EventEmitter
  • EventEmitter.on(event, listener)
  • EventEmitter.addListener(event, listener)
  • EventEmitter.emit(event, [args...])
  • EventEmitter.removeListener(event, listener)
  • EventEmitter.removeAllListeners(event)
  • EventEmitter.eventNames()
  • EventEmitter.getMaxListeners()
  • EventEmitter.listeners(event)
  • EventEmitter.setMaxListeners(max)
• Sample Apps

Introduction

ZJS provides event APIs that match Node.js Events. We describe them here as there could be minor differences.

Web IDL

This IDL provides an overview of the interface; see below for documentation of specific API functions. We also have a short document explaining ZJS WebIDL conventions.

Click to show/hide WebIDL

callback ListenerCallback = void (any... params);
interface EventEmitter {
    this on(string event, ListenerCallback listener);
    this addListener(string event, ListenerCallback listener);
    boolean emit(string event, any... args);
    this removeListener(string event, ListenerCallback listener);
    this removeAllListeners(string event);
    sequence < string > eventNames();
    long getMaxListeners();
    sequence < ListenerCallback > listeners(string event);
    this setMaxListeners(long max);
};

EventEmitter API

EventEmitter.on(event, listener)

• event string The name of the event that you are adding a listener to.
• listener ListenerCallback The function that you wish to be called when this event is emitted/triggered.
• Returns: this so calls can be chained.

Add an event listener function.

EventEmitter.addListener(event, listener)

• event string The name of the event that you are adding a listener to.
• listener ListenerCallback The function that you wish to be called when this event is emitted/triggered.
• Returns: this so calls can be chained.

Same as EventEmitter.on().

EventEmitter.emit(event, [args...])

• event string The name of the event that you want to emit.
• args optional All other arguments will be given to any registered listener functions.
• Returns: true if there were any listener functions called.

Triggers an event. Any listener functions that have been added to the event emitter under the event name will be called.

EventEmitter.removeListener(event, listener)

• event string The name of the event you are removing the listener from.
• listener ListenerCallback The function you want to remove as a listener.
• Returns: this so calls can be chained.

Removes a listener function from an event.

EventEmitter.removeAllListeners(event)

• event string The name of the event from which to remove all listeners.
• Returns: this so calls can be chained.

Removes all listeners from an event

EventEmitter.eventNames()

• Returns: an array of strings that correspond to any events. Will return undefined if there are no event's or event listeners for this event emitter.

Get a list of event names from an event emitter object.

EventEmitter.getMaxListeners()

• Returns: the maximum number of listeners allowed.

Get the maximum number of listeners allowed for this event emitter object.

EventEmitter.listeners(event)

• event string The name of the event from which to retrieve the listerners.
• Returns: an array of functions that correspond to the ListenerCallbacks for the event specified.

Get a list of listeners for an event.

EventEmitter.setMaxListeners(max)

• max long The number of listeners the event emitter can have.
• Returns: this, so calls can be chained.

Set the max number of listeners for an event emitter object

Sample Apps

• Events sample