Reactive forms provide a model-driven approach to handling form inputs whose values change over time. This architecture is built around observable streams.
1Immutable Form State
Unlike template-driven forms, where the state is managed implicitly by directives, reactive forms give you an explicit object representing the form state. This state is predictable and can be accessed or modified programmatically at any time. Because the form structure is defined in code, you can easily perform complex validations that depend on multiple fields or dynamic data from an API.
2The Power of Observables
Every FormControl and FormGroup in a reactive form has a valueChanges property. This is an Observable that emits a new value every time the input changes. This allows you to react to user input in real-time—for example, to perform a live search, auto-calculate totals, or show/hide sections of the form based on previous answers—without writing complex event listeners.
