Question

What are controlled components in ReactJS?

Answer 1

A component that controls the input elements within the forms on subsequent user input is called Controlled Component, i.e, every state mutation will have an associated handler function.

For example, to write all the names in uppercase letters, we use handleChange as below,

handleChange(event) {
  this.setState({value: event.target.value.toUpperCase()})
}

Answer 2

Controlled components are component which controls the input elements.