How to display username on navbar after login in react redux - reactjs

Question

There is a nav link on my navbar named Login (I have used bootstrap navbar). After successful login I want to replace Login with a username using react-redux (not redux-toolkit).
Kindly help me in writing reducer and action code. As I am a beginner in redux and I don't know how to code in reducer and action file it is very confusing for me.
Navbar component (Navbar.js)
import React from 'react';
import { Link } from 'react-router-dom';
import { useSelector } from 'react-redux';
const Navbar = () => {
const {username} = useSelector((state) => state.user);
return (
<div>
<nav className="navbar navbar-expand-lg">
<div className="container-fluid">
<Link className="navbar-brand" to="/hommepage">Ebuy</Link>
<button className="navbar-toggler" type="button" data-bs-toggle="collapse" data-bs-target="#navbarSupportedContent" aria-controls="navbarSupportedContent" aria- expanded="false" aria-label="Toggle navigation">
<span className="navbar-toggler-icon">
<i className="fas fa-bars" style={{color: 'white', fontSize: '28px'}}></i>
</span>
</button>
<div className="collapse navbar-collapse" id="navbarSupportedContent">
<ul className="navbar-nav me-auto mb-2 mb-lg-0">
<li className="nav-item">
<Link className="nav-link" aria-current="page" to="/homepage">Home</Link>
</li>
<li className="nav-item dropdown">
<Link className="nav-link dropdown-toggle" to="#" id="navbarDropdown" role="button" data-bs-toggle="dropdown" aria-expanded="false">
Select Category
</Link>
<ul className="dropdown-menu" aria-labelledby="navbarDropdown">
<li><Link className="dropdown-item" to="/skincare">Skincare Products</Link></li>
<li><Link className="dropdown-item" to="/stationary">Stationary Products</Link></li>
<li><Link className="dropdown-item" to="#">Clothing</Link></li>
</ul>
</li>
</ul>
<div className="d-flex">
<ul className="navbar-nav me-auto mb-2 mb-lg-0">
<li className='nav-item'>
<Link className="nav-link" to="/">Login</Link>
</li>
</ul>
</div>
</div>
</div>
</nav>
</div>
);
};
export default Navbar;

Answer 1

reducer
const initialState = {
username: null,
}
export const userReducer(state = initialState, action) {
switch (action.type) {
case "CHANGE_USERNAME":
return {
...state,
username: action.payload,
}
default:
return state
}
}
action
export const changeUserName = (name) => {
return {
type: "CHANGE_USERNAME",
payload: name
}
}
after login call this
const dispatch = useDispatch()
const login = () => {
... login logic here
dispatch(changeUserName("user-1"))
}
in navbar
const { username } = useSelector(state=> state.user)

Answer 2

In your Navbar Component you should get username from redux, please try this :
const {username} = useSelector(state=> state.yourReducerName)
after this, in your jsx : you should write a condition like this :
{username ? (<div>{username}</div>): ()<span>Login</span>}
EDIT :
Please refer to this sandbox example and take a look on the reducer and actions files, also on the navbar components.
Let us know if the post helped you :)