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  1. Sep 2020
    1. Q7. What are controlled components?In HTML, form elements such as <input>, <textarea>, and <select> typically maintain their own state and update it based on user input. When a user submits a form the values from the aforementioned elements are sent with the form. With React it works differently. The component containing the form will keep track of the value of the input in it's state and will re-render the component each time the callback function e.g. onChange is fired as the state will be updated. A form element whose value is controlled by React in this way is called a "controlled component".With a controlled component, every state mutation will have an associated handler function. This makes it straightforward to modify or validate user input.

      In classical HTML form components such as <input> or <textarea> maintain their own state, which gets sent somewhere upon submission of the form.

      React keeps track of the form's state inside a component and will re-render the component when the state changes. This can be listened to by subscribing to the onChange callback function.