What is the purpose of updateOn in Reactive Forms?

Q: What is the purpose of updateOn in Reactive Forms?

**Core concept.** ** updateOn ** is a configuration property that controls when validation and value updates propagate through FormControls. By default, it updates on every keystroke ( 'change' ). Changing it to 'blur' or 'submit' defer validation checks until focus is lost or the form is submitted. ### updateOn Configurations - ** 'change' (Default):** Propagates value and validation status instantly on every input stroke. - ** 'blur' :** Propagates only when the user shifts focus away from the input element. Great for server validation (e.g. checking unique usernames). - ** 'submit' :** Propagates only when the parent form element triggers a submit event. Best for performance-intensive forms. > **Interview tip:** Frame updateOn: 'blur' as a performance optimization. If you have async validators checking username availability against a backend API, setting updateOn to 'b

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**Core concept.** **updateOn** is a configuration property that controls when validation and value updates propagate through FormControls. By default, it updates on every keystroke ('change'). Changing it to 'blur' or 'submit' defer validation checks until focus is lost or the form is submitted. ### updateOn Configurations - **'change' (Default):** Propagates value and validation status instantly on every input stroke. - **'blur':** Propagates only when the user shifts focus away from the input element. Great for server validation (e.g. checking unique usernames). - **'submit':** Propagates only when the parent form element triggers a submit event. Best for performance-intensive forms. > **Interview tip:** Frame updateOn: 'blur' as a performance optimization. If you have async validators checking username availability against a backend API, setting updateOn to 'b

What is the purpose of updateOn in Reactive Forms?

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