Class EventTable

Object
   |
   +--EventTable

class EventTable

Defined in event_table.js

Constructor Detail

EventTable

function EventTable(<Array> eventList)

Creates an event table that can map event names to functions to be called when those events are raised.

Parameters:
eventList - a list of strings, each of which is the name of an event that this table should govern

addEventListener

boolean addEventListener(<string> event, <Function> listener)

Registers a listener for the named event. Does nothing if listener has already been registered for the event named event. Note that this condition is checked with the equality operator, so two functions that do the same thing but are different instances of the Function class can both be registered for the same event, and both will be called when the event is raised.

For example, the following code will generate 5 alert boxes:

var eventTable = new EventTable(['alert']);

for(var i = 0; i < 5; ++i) {
    eventTable.addEventListener('alert', function() {
        alert('The event named "alert" was raised');
    });
}

eventTable.raiseEvent('alert', null);

whereas the following code will only generate one alert box:

var eventTable = new EventTable(['alert']);

function showAlert() {
    alert('The event named "alert" was raised');
}

for(var i = 0; i < 5; ++i) {
    eventTable.addEventListener('alert', showAlert);
}

eventTable.raiseEvent('alert', null);

Parameters:
event - the name of the event to which listener should be attached
listener - a function to be called whenever the event named event is raised. There is no guarantee about the order in which listeners are called for a given event. listener can be passed one argument. This argument depends on the semantics of the event and is passed indirectly by the event raiser.

Returns:
true if listener was added and false if not. A listener will not be added a second time to the same event.

addEventType

void addEventType(<string> event)

Adds the named event to the list of events in this table. Does nothing if there is already such an event in the table.

Parameters:
event - the name of the event to add

hasEvent

boolean hasEvent(<string> event)

Returns true if this event table has an event named event.

Parameters:
event - the name of the event to check for

Returns:
true if this event table has an event named event and false if not

raiseEvent

void raiseEvent(<string> eventName, <Object> eventObj)

Raises the event named eventName and passes eventObj to all registered listeners. Note that if any of the listeners cause this instance of EventTable to raise the same event as is currently being raised (directly or indirectly), the secondary attempts will be ignored—this is to avoid infinite loops like the following (ie. the following example will terminate because EventTable blocks the raiseEvent call that is made inside the listener):

var eventTable = new EventTable(['infinite']);

// register a listener that raises the event currently being raised
eventTable.addEventListener('infinite', function() {
    eventTable.raiseEvent('infinite', null);
});

// initiate the infinite loop
eventTable.raiseEvent('infinite', null);

Parameters:
eventName - the name of the event to raise. This event table must have an event by this name or an exception will be thrown.
eventObj - (Optional) - an argument to pass to all listeners registered for this event. EventTable imposes no meaning or restrictions on eventObj.

removeEventListener

boolean removeEventListener(<string> event, <Function> listener)

Deregisters a listener from the named event. Does nothing if listener wasn't registered for event in the first place.

Parameters:
event - the name of the event from which listener should be deregistered
listener - the function that should no longer be called when the event named event is raised

Returns:
true if listener was deregistered and false if not.

toString

string toString()

Returns a string representation of this event table for debugging purposes.

Returns:
a string representation of this event table