custom hook useLocalStorage

react-advanced-tag1/src/components/exercises/RefExercise/index.tsx

@@ -1,16 +1,30 @@
 import { FormEvent, useRef, useState } from "react";
+import useLocalStorage from "../../../hooks/useLocalStorage";
+
+interface FormValues {
+    email: string;
+    password: string;
+}
 
 export default function RefExercise(): React.ReactElement {
     console.log("RefExercise rendered");
 
     const emailRef = useRef<HTMLInputElement>(null);
     const passwordRef = useRef<HTMLInputElement>(null);
+    const {setStoredValue, value: formDataValues} = useLocalStorage<FormValues>("formdata", {
+        email: "",
+        password: ""
+    } );
 
     const handleSubmit = () => {
         console.log("submit", {
             email: emailRef.current?.value,
             password: passwordRef.current?.value
         });
+        setStoredValue({
+            email: emailRef.current?.value || "",
+            password: passwordRef.current?.value || ""
+        });
         passwordRef.current?.focus();
     }
 
@@ -47,8 +61,8 @@ export default function RefExercise(): React.ReactElement {
         <div style={{ display: "flex", flexDirection: "column", gap: "3rem" }}>
         <div style={{ display: "flex", flexDirection: "column", gap: "1rem" }}>
             <h3>values by ref</h3>
-            <input type="text" placeholder="email" ref={emailRef}/>
-            <input type="text" placeholder="password" ref={passwordRef}/>
+            <input type="text" placeholder="email" ref={emailRef} defaultValue={formDataValues?.email}/>
+            <input type="text" placeholder="password" ref={passwordRef} defaultValue={formDataValues?.password}/>
             <button onClick={handleSubmit}>Submit</button>
         </div>
         <div style={{ display: "flex", flexDirection: "column", gap: "1rem" }}>

react-advanced-tag1/src/components/exercises/UserEffect.tsx

@@ -19,6 +19,8 @@ export default function UserEffect() {
             return;
         }
 
+        const start = performance.now(); // Start measuring performance
+
         setLoading(true);
 
         // Using AbortController to cancel the fetch request if the component unmounts
@@ -33,6 +35,9 @@ export default function UserEffect() {
             return response.json();
         }).then(data => {
             setUser(data);
+            const end = performance.now(); // End measuring performance
+            const timeTaken = end - start; // Calculate the time taken
+            console.log(`Fetch completed in ${Math.round(timeTaken)} milliseconds`);
             setLoading(false);
         }).catch(error => {
             console.error("There was a problem with the fetch operation:", error);

react-advanced-tag1/src/components/exercises/UserOverview.tsx

@@ -1,8 +1,13 @@
 import { useFetch } from "../../hooks/useFetch";
+import { useMediaQuery } from "../../hooks/useMediaQuery";
 
 export function UserOverview() {
     const {data, loading, error} = useFetch("https://jsonplaceholder.typicode.com/users");
 
+    const isMobile = useMediaQuery('(max-width: 600px)');
+
+    console.log("isMobile", isMobile);
+
     if (error) {
         return <p>Error: {error}</p>;
     }
@@ -18,7 +23,7 @@ export function UserOverview() {
             <ul>
                 {data.map((user: { id: number; name: string; email: string; website: string }) => (
                     <li key={user.id}>
-                        <strong>{user.name}</strong> ({user.email}) - {user.website}
+                        <strong>{user.name}</strong> <div style={{display: isMobile ? 'none' : 'block' }}>({user.email}) - {user.website}</div>
                     </li>
                 ))}
             </ul>

react-advanced-tag1/src/hooks/useLocalStorage.ts

@@ -0,0 +1,39 @@
+import { useState } from "react";
+
+export default function useLocalStorage<T>(key: string, initialValue: T | null) {
+    const [value, setValue] = useState<T | null>(() => {
+        try {
+            if (typeof window === "undefined") {
+                return initialValue;
+            }
+            const storedValue = localStorage.getItem(key);
+            return storedValue ? JSON.parse(storedValue) : initialValue;
+        } catch (error) {
+            console.error("Error reading from localStorage", error);
+            return initialValue;
+        }
+    });
+    const setStoredValue = (newValue: T) => {
+        try {
+            const valueToStore = newValue instanceof Function ? newValue(value) : newValue;
+            setValue(valueToStore);
+            if (typeof window !== "undefined") {
+                localStorage.setItem(key, JSON.stringify(valueToStore));
+            }
+        } catch (error) {
+            console.error("Error writing to localStorage", error);
+        }
+    }
+
+    const removeStoredValue = () => {
+        try {
+            if (typeof window !== "undefined") {
+                localStorage.removeItem(key);
+            }
+            setValue(null);
+        } catch (error) {
+            console.error("Error removing from localStorage", error);
+        }
+    }
+    return {value, setStoredValue, removeStoredValue};
+}

react-advanced-tag1/src/hooks/useMediaQuery.ts

@@ -0,0 +1,31 @@
+import { useEffect, useState } from "react";
+
+
+/**
+ * Custom hook to check if a media query matches the current viewport.
+ * @param query - The media query string (e.g., '(max-width: 600px)')
+ * @returns A boolean indicating whether the media query matches.
+ */
+export function useMediaQuery(query: string) {
+    const [matches, setMatches] = useState<boolean>(false);
+
+    useEffect(() => {
+        const mediaQueryList = window.matchMedia(query);
+        const handleChange = (event: MediaQueryListEvent) => {
+            setMatches(event.matches);
+        };
+
+        // Set the initial value
+        setMatches(mediaQueryList.matches);
+
+        // Add event listener
+        mediaQueryList.addEventListener('change', handleChange);
+
+        // Cleanup function to remove the event listener
+        return () => {
+            mediaQueryList.removeEventListener('change', handleChange);
+        };
+    }, [query]);
+
+    return matches;
+}