SubscribableMap

SubscribableMap, as the name suggests, extends the Map class and calls a function when a value is changed.

Installation

npm i -S subscribablemap

Usage

SubscribableMap extends the Map class, so the same API is available. However, overridden methods may work slightly differently to the Map API. The following methods have also been added:

• subscribe(fn, [bypassCooldown]): Subscribes to changes. By default, the cooldown is respected when emitting events. This can be changed by setting bypassCooldown to false.
• unsubscribe(fn): Unsubscribes from change events.
• getSubscribers(): Gets the subscriber Set
• getOpts(): Gets the options passed in the constructor
• serialize(): Returns a key-value array ([ ['key', 'value'] ]) from the data in the Map

The constructor takes the following options object:

• cooldown: By setting this option, you can restrict SubscribableMap to only sending one event per key per time specified (in milliseconds) here.
• deleteBypassesCooldown: By default, delete()/clear() bypass the cooldown. You can change this option so that delete() does not bypass the cooldown.
• forceEmitAfterCooldownIfChanged: By setting this to true, a sync event will be emitted after the cooldown if the data has changed during the cooldown period. Note that this event may be up to 100ms late.
• initialValue: If you'd like to initialize the Map with values, you can pass them here as a key-value array.

const SubscribableMap = require('subscribablemap');

let map = new SubscribableMap();

map.subscribe((s) => {
	// Returns: { event: 'set', key: 'test', value: 'ing' }
	// Key will be undefined if this is a clear event.
	// Value will be undefined if this is a clear/delete event.

	// If you have different code for different events, it is
	// advisable to check if the event equals an enum in
	// SubscribableMap.enum (e.g. s.event === SubscribableMap.enum.SET).

	console.log(s);
});

map.set('test', 'ing');

Important: Only the set(), delete(), clear() methods will dispatch events. You can pass a boolean set to false as the last parameter to these methods to suppress the event for that update. Note that sync events (enabled with the forceEmitAfterCooldownIfChanged option) will still be dispatched even for suppressed updates.