Introduction:

useReducer hook in react is used for state management. This hook is implemented in large projects where there is a need for managing multiple states.

The syntax for this hook is : useReducer(reducer,initialState)This takes two arguments as input. The first argument is the reducer function and the second argument is an initial state and returns a pair of values [state, dispatch]

The reducer function is a pure function which means it generates only direct results. It takes two parameters current state and action and must return a value.

useReducer hook in Counter:

import React,{useReducer} from "react";

const initialState =0;
const reducer =(state,action)=>{
    if(action.type==='increment')
        return state+1;
    if(action.type ==='decrement')
        return state-1;
  return state;
}

const UseReduce =()=>{
    const [state,dispatch] = useReducer(reducer,initialState);
    return(
      <>
        <div>
          <p>{state}</p>
          <div>
            <button onClick={() => dispatch({type:'increment'})}>Increment</button>
            <button onClick={() => dispatch({type:'decrement'})}>Decrement</button>
          </div>

        </div>
      </>
      )}
export default UseReduce;

Here the dispatch triggers the action method of the reducer function and sends the type of action as a parameter. Based on action type the operations are conditionally performed.