Answer
The observer pattern allows objects to subscribe to changes in another object.
Useful for events, data binding, and reactive programming.
Quick Answer
Observer Pattern: an object (subject) maintains a list of subscribers (observers) and notifies them when its state changes. Events in the browser ARE the Observer pattern — addEventListener is subscribe, dispatchEvent is notify. Custom implementation: EventEmitter with on(), emit(), and off(). Enables decoupled, reactive systems.
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SugharaIQ Editorial Team
Verified Answer
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Source: SugharaIQ