react.dev/cookbook/cb-08-controlled-input-null-value.md

id	title	layout	permalink
controlled-input-null-value	Value of null for controlled input	docs	controlled-input-null-value.html

Problem

You specified a value parameter for your form input, but the input value can still be modified, contrary to what you'd expect.

Solution

You might have accidentally set your value to undefined or null. The snippet below shows this phenomenon; after a second, the text can be edited.

/** @jsx React.DOM */

React.renderComponent(<input value="hi" />, mountNode);

setTimeout(function() {
  React.renderComponent(<input value={null} />, mountNode);
}, 2000);