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Classes

EventEmitter
EventHandler

EventEmitter

new EventEmitter() (constructor)
.on(name, callback, [scope], [once]) ⇒ EventHandler
.once(name, callback, [scope]) ⇒ EventHandler
.emit(name, [...args])
.off([name], [callback], [scope])

new EventEmitter()

Provides ability to subscribe and emit events in sync manner. Each subscribtion (on, once) returns EventHandler that simplifies callbacks management.

Example

const world = new EventEmitter();

world.on('event', function (number) {
    console.log('event', number);
});

world.emit('event', 42);

.on(name, callback, [scope], [once]) ⇒ EventHandler

Attach an event handler.

Returns: EventHandler - Object that can be used to manage the event.

Param Type Description
name string Name of the event to bind the callback to.
callback function Function that is called when event is emitted.
[scope] object Object to use as 'this' when the event is emitted, defaults to current this.
[once] boolean Boolean to indicate if this event should emit only once. Defaults to false.

Example

obj.on('event', function (a, b) {
    console.log(a + b);
});
obj.emit('event', 4, 2);

.once(name, callback, [scope]) ⇒ EventHandler

Attach an event handler which will emit only once.

Returns: EventHandler - Object that can be used to manage the event.

Param Type Description
name string Name of the event to bind the callback to.
callback function Function that is called when event is emitted.
[scope] object Object to use as 'this' when the event is emitted, defaults to current this.

Example

obj.once('event', function (a) {
    console.log(a);
});
obj.emit('event', 4);
obj.emit('event', 2); // will not trigger

.emit(name, [...args])

Emit the event by name and optional list of arguments.

Param Type Description
name string Name of the event to bind the callback to.
[...args] * Arguments to be passed to event callbacks.

Example

obj.emit('event', 'hello', 42);

.off([name], [callback], [scope])

Remove event handlers based on provided arguments.

Param Type Description
[name] string Name of the events to remove. If not specified all events will be removed.
[callback] function Function that is used as callback. If not defined, then all events of specified name will be removed.
[scope] object Object that is used as a scope for event handlers. If not defined, then all events with matching name and callback function will be removed.

Example

obj.off(); // removes all events
obj.off('event'); // removes all events named `event`.
obj.off(/input:\w+/); // removes all events with name matching regular expression
obj.off('event', fn); // removes events named `event` with `fn`
obj.off('event', fn, obj); // removes events named `event` with `fn` callback and `obj` as a scope.

EventHandler

new EventHandler() (constructor)
.emit([...args])
.off()

new EventHandler()

Constructed by EventEmitter and provides easy ability to manage event.

.emit([...args])

Emit the event with optional list of arguments.

Param Type Description
[...args] * Arguments to be passed to event callbacks.

Example

evt.emit(42, 'hello');

.off()

Removes event from EventEmitter.

Example

evt.off();