[Home](./index.md) > [sip.js](./sip.js.md) > [Emitter](./sip.js.emitter.md) ## Emitter interface Generic observable. Signature: ```typescript export interface Emitter ``` ## Methods | Method | Description | | --- | --- | | [addListener(listener, options)](./sip.js.emitter.addlistener.md) | Sets up a function that will be called whenever the target changes. | | [off(listener)](./sip.js.emitter.off.md) | Unregisters a listener. | | [on(listener)](./sip.js.emitter.on.md) | Registers a listener. | | [once(listener)](./sip.js.emitter.once.md) | Registers a listener then unregisters the listener after one event emission. | | [removeListener(listener)](./sip.js.emitter.removelistener.md) | Removes from the listener previously registered with addListener. |