Posted on Sep 28 When learning Angular and delving into the reactive programming paradigm, it's easy to stumble upon terms that may seem intimidating—Observable, Subject, BehaviorSubject, and so on. Today, we're going to demystify one of these terms: BehaviorSubject.Angular relies heavily on reactive programming patterns, particularly those provided by the RxJS library. Reactive programming is all about dealing with asynchronous operations and data streams. This is where BehaviorSubject comes in as a powerful construct for managing these streams.A BehaviorSubject is a type of subject, a particular kind of observable in RxJS. What makes it unique is that it stores the "current" value. This means that when you subscribe to it, you immediately get the latest emitted value—or a default value if none has been emitted yet.In the code above, temperature$ is a BehaviorSubject that starts with an initial value of 20. The $ at the end is a naming convention often used for Observables.Think of BehaviorSubject as a digital thermometer in a room. Various departments in an organization—say, Maintenance, Operations, and HR—need to know the room's temperature.When you set up the thermometer, you determine that the initial temperature is 20°C. This initial value is crucial for any department that decides to monitor the temperature.Maintenance and Operations departments 'subscribe' to the thermometer. From that point on, they get updated readings whenever the temperature changes.Now, HR also decides to subscribe. The moment they do, they receive the current temperature, not the initial one.To change the thermometer's reading, you use the next() method. This action updates the current value and informs all subscribers about this change.This will log:The next() function effectively pushes the new value into the BehaviorSubject, updating all active subscribers.You might ask, "How is this different from an Observable?" The crucial difference lies in the initial value and the immediate availability of the current value. With a standard Observable, new subscribers would have to wait for a new value to be emitted. They don't get the latest value right when they subscribe, as with BehaviorSubject.Understanding BehaviorSubject can significantly impact how you manage state and data flow in Angular applications. The ability to emit, listen, and react to new data points in different parts of your application is not just powerful; it also aligns closely with Angular's reactive ethos.With this newfound knowledge, you're one step closer to mastering Angular's reactive landscape. Happy coding!Templates let you quickly answer FAQs or store snippets for re-use. Are you sure you want to hide this comment? It will become hidden in your post, but will still be visible via the comment's permalink. Hide child comments as well Confirm For further actions, you may consider blocking this person and/or reporting abuse Francisco Inoque - Sep 25 shrey vijayvargiya - Sep 17 Emily Thompson - Sep 26 Joy Winter - Sep 13 Once suspended, petermilovcik will not be able to comment or publish posts until their suspension is removed. Once unsuspended, petermilovcik will be able to comment and publish posts again. Once unpublished, all posts by petermilovcik will become hidden and only accessible to themselves. If petermilovcik is not suspended, they can still re-publish their posts from their dashboard. Note: Once unpublished, this post will become invisible to the public and only accessible to PeterMilovcik. They can still re-publish the post if they are not suspended. Thanks for keeping DEV Community safe. Here is what you can do to flag petermilovcik: petermilovcik consistently posts content that violates DEV Community's code of conduct because it is harassing, offensive or spammy. Unflagging petermilovcik will restore default visibility to their posts. DEV Community — A constructive and inclusive social network for software developers. With you every step of your journey. Built on Forem — the open source software that powers DEV and other inclusive communities.Made with love and Ruby on Rails. DEV Community © 2016 - 2023. We're a place where coders share, stay up-to-date and grow their careers.