Code Programming Tutorials, Guides & Best Practices

const express = require('express');
const { ApolloServer, gql } = require('apollo-server-express');

// Sample data
let books = [
    { title: 'The Great Gatsby', author: 'F. Scott Fitzgerald' },
    { title: 'To Kill a Mockingbird', author: 'Harper Lee' },
];

// GraphQL schema definition
const typeDefs = gql`
    type Book {
        title: String!
        author: String!
    }

    type Query {
        books: [Book]
    }

    type Mutation {
        addBook(title: String!, author: String!): Book
    }
`;

// GraphQL resolvers
const resolvers = {
    Query: {
        books: () => books,
    },
    Mutation: {
        addBook: (_, { title, author }) => {
            const newBook = { title, author };
            books.push(newBook);
            return newBook;
        },
    },
};

// Create Apollo server
const server = new ApolloServer({ typeDefs, resolvers });

const app = express();
server.applyMiddleware({ app });

app.listen({ port: 4000 }, () =>
    console.log(` Server ready at http://localhost:4000${server.graphqlPath}`)
);

• Schema Definition: The typeDefs defines a simple schema with a Book type and queries to fetch books and add a new book.
• Resolvers: Functions that resolve the queries and mutations. In this case, they return all books and add a new book to the list.

import { useState, useEffect } from 'react';

function useFetch(url, options = {}) {
    const [data, setData] = useState(null);
    const [loading, setLoading] = useState(true);
    const [error, setError] = useState(null);

    useEffect(() => {
        let isMounted = true; // Track if component is mounted

        const fetchData = async () => {
            setLoading(true);
            try {
                const response = await fetch(url, options);
                if (!response.ok) {
                    throw new Error('Network response was not ok');
                }
                const result = await response.json();
                if (isMounted) {
                    setData(result);
                }
            } catch (error) {
                if (isMounted) {
                    setError(error);
                }
            } finally {
                if (isMounted) {
                    setLoading(false);
                }
            }
        };

        fetchData();

        return () => {
            isMounted = false; // Cleanup to avoid setting state on unmounted component
        };
    }, [url, options]);

    return { data, loading, error };
}

export default useFetch;

Here’s an example of how to use the useFetch hook in a React component to fetch and display data.