Performance optimizations

- React lazy and Suspense added to router components
- added memo to some components
- added useCallback to some functions

README.md

@@ -28,6 +28,10 @@ My React experience has been on and off as my career led to be a Senior Frontend
 - Shop / Category pages with functional Add To Cart button + Minicart + Bag icon counter
 - Cart/Minicart quantity changes + product removal + counter update
 - Categories data comes from Firebase.
+- Code performance improvements:
+  - added `useCallback` to avoid redefininig functions;
+  - added `memo` to some components to avoind unnecessary re-renders;
+  - added react `lazy` and `Suspense` to App for better bundle/code splitting;
 
 ## Extra features / learning by me (not part of the course)
 - Products have currency and proper price format.

src/App.jsx

@@ -1,15 +1,16 @@
-import { useEffect } from 'react';
+import { useEffect, lazy, Suspense } from 'react';
 import { Routes, Route } from "react-router-dom";
 import { useDispatch } from 'react-redux';
 
 import { authChangedListener, createUserDocFromAuth } from './utils/firebase/firebase.utils.js';
 import { setCurrentUser } from './store/user.reducer.js';
+import SpinnerComponent from './components/spinner/spinner.component.jsx';
 
-import Navigation from './routes/navigation/navigation.component.jsx';
-import Home from './routes/home/home.component';
-import Login from './routes/login/login.component.jsx';
-import Shop from './routes/shop/shop.component.jsx';
-import CheckoutComponent from './routes/checkout/checkout.component.jsx';
+const Navigation = lazy(() => import('./routes/navigation/navigation.component'));
+const Home = lazy(() => import('./routes/home/home.component'));
+const Login = lazy(() => import('./routes/login/login.component'));
+const Shop = lazy(() => import('./routes/shop/shop.component'));
+const CheckoutComponent = lazy(() => import('./routes/checkout/checkout.component'));
 
 const App = () => {
 
@@ -27,14 +28,17 @@ const App = () => {
   }, []); // eslint-disable-line react-hooks/exhaustive-deps
 
   return (
-    <Routes>
-      <Route path='/' element={<Navigation />}>
-        <Route index element={<Home />} />
-        <Route path='shop/*' element={<Shop />} />
-        <Route path='login' element={<Login />} />
-        <Route path='checkout' element={<CheckoutComponent />} />
-      </Route>
-    </Routes>
+    <Suspense fallback={<SpinnerComponent />}>
+
+      <Routes>
+        <Route path='/' element={<Navigation />}>
+          <Route index element={<Home />} />
+          <Route path='shop/*' element={<Shop />} />
+          <Route path='login' element={<Login />} />
+          <Route path='checkout' element={<CheckoutComponent />} />
+        </Route>
+      </Routes>
+    </Suspense>
   )
 }
 

src/components/cart/cart-icon.component.jsx

@@ -5,15 +5,16 @@ import { toggleMinicart } from '../../store/minicart.reducer';
 
 import bagIcon from '../../assets/shopping-bag.svg'
 import './cart-icon.styles.scss';
+import { useCallback } from 'react';
 
 const CartIcon = () => {
   const dispatch = useDispatch();
   const bagCount = useSelector(selectBagCount);
   const openMinicart = useSelector(selectOpenMinicart);
 
-  const handleMinicartToggle = () => {
+  const handleMinicartToggle = useCallback(() => {
     dispatch(toggleMinicart(!openMinicart));
-  }
+  }, [openMinicart]); //eslint-disable-line react-hooks/exhaustive-deps
 
   return (
     <button type='button' className='cart-icon-container' onClick={handleMinicartToggle}>

src/components/cart/cart-item.component.jsx

@@ -1,6 +1,9 @@
+import { memo } from 'react';
+
 import './cart-item.styles.scss';
 
-const CartItem = ({ cartItem }) => {
+// eslint-disable-next-line react/display-name
+const CartItem = memo(({ cartItem }) => {
   const { name, imageUrl, price, quantity } = cartItem;
   return (
     <div className='minicart-item'>
@@ -14,6 +17,6 @@ const CartItem = ({ cartItem }) => {
       </div>
     </div>
   );
-}
+})
 
 export default CartItem;

src/components/cart/minicart.component.jsx

@@ -1,4 +1,4 @@
-import { useEffect } from 'react';
+import { memo, useCallback, useEffect } from 'react';
 import { useSelector, useDispatch } from 'react-redux';
 import { Link, useLocation } from 'react-router-dom';
 
@@ -8,7 +8,8 @@ import { toggleMinicart } from '../../store/minicart.reducer';
 import CartItem from './cart-item.component.jsx';
 import './minicart.styles.scss';
 
-const Minicart = () => {
+// eslint-disable-next-line react/display-name
+const Minicart = memo(() => {
   const dispatch = useDispatch();
   const location = useLocation();
   const openMinicart = useSelector(selectOpenMinicart);
@@ -21,9 +22,9 @@ const Minicart = () => {
     }
   }, [location]); //eslint-disable-line react-hooks/exhaustive-deps
 
-  const closeMinicart = () => {
+  const closeMinicart = useCallback(() => {
     dispatch(toggleMinicart(false))
-  }
+  }, []);//eslint-disable-line react-hooks/exhaustive-deps
 
   return (
     <div
@@ -53,6 +54,6 @@ const Minicart = () => {
       </div>
     </div>
   );
-}
+})
 
 export default Minicart;

src/components/login-form/login-form.component.jsx

@@ -1,4 +1,4 @@
-import { useState } from 'react';
+import { useCallback, useState } from 'react';
 import {
   signInWithGooglePopup,
   loginUserWithEmailPwd
@@ -16,13 +16,13 @@ const LoginForm = () => {
   const [formFields, setFormFields] = useState(defaultFormFields);
   const { email, password } = formFields;
 
-  const clearForm = () => {
+  const clearForm = useCallback(() => {
     setFormFields(defaultFormFields);
-  };
+  }, []);
 
-  const loginWithGoogle = async () => {
+  const loginWithGoogle = useCallback(async () => {
     await signInWithGooglePopup();
-  };
+  }, []);
 
   const handleSubmit = async (event) => {
     event.preventDefault();

src/components/register-form/register-form.component.jsx

@@ -1,4 +1,4 @@
-import { useState } from 'react';
+import { useCallback, useState } from 'react';
 import FormInput from '../form-input/form-input.component';
 import Button from '../button/button.component';
 import { createUserWithEmailPwd, createUserDocFromAuth } from '../../utils/firebase/firebase.utils';
@@ -18,12 +18,12 @@ const RegisterForm = () => {
   // Destructure the passed object above to have their values as variables
   const { displayName, email, password, confirmPassword } = formFields;
 
-  const clearForm = () => {
+  const clearForm = useCallback(() => {
     setFormFields(defaultFormFields);
-  };
+  }, []);
 
   // Handle the submit, async as it uses external auth
-  const handleSubmit = async (event) => {
+  const handleSubmit = useCallback(async (event) => {
     event.preventDefault();
 
     //Verify is password matches, can extend this to add more checks like format, length,etc
@@ -49,7 +49,7 @@ const RegisterForm = () => {
         console.log(`User creation error: ${error.message}`)
       }
     }
-  };
+  }, [formFields]); //eslint-disable-line react-hooks/exhaustive-deps
 
   // Basic function called by the inputs onChange event
   const handleChange = (event) => {