> For the complete documentation index, see [llms.txt](https://bharat-tiwari.gitbook.io/our-tech-journal/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://bharat-tiwari.gitbook.io/our-tech-journal/angular-4/observable-vs-subject/behaviorsubject.md).

# BehaviorSubject

One of the variants of Subjects is the BehaviorSubject, which has a notion of "the current value". It stores the latest value emitted to its consumers, and whenever a new Observer subscribes, it will immediately receive the "current value" from the BehaviorSubject.

BehaviorSubjects are useful for representing "values over time". For instance, an event stream of birthdays is a Subject, but the stream of a person's age would be a BehaviorSubject.


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