To store the previous value of a state in React, you can create a new state variable to store the previous value, and update it when the component's state changes. Here's an example of how you might do this:

In this example, the component has a state variable called value that is used to store the current value of the input field, and a state variable called prevValue that is used to store the previous value of the input field. When the input field is changed, the handleChange function is called, which updates both the value and prevValue state variables using the setState method. The prevValue is updated to the current value of value, and then value is updated to the new value from the input field. This way, the previous value of the input field is always stored in the prevValue state variable.