GraphQL

GraphQL is a query language for APIs and a server-side runtime for executing queries by providing a complete and understandable description of your data. Unlike REST, which uses multiple endpoints, GraphQL uses a single endpoint to handle all queries and mutations.

🤔 Why use GraphQL?

• Flexible Queries: Clients can request exactly the data they need.
• Single Endpoint: Reduces complexity and improves performance.
• Strongly Typed Schema: Ensures a clear contract between client and server.

🛠️ Getting started with GraphQL

📚 Basics

• Queries: Fetch data from the server.
• Mutations: Modify data on the server.
• Schema: Defines the structure of the data and the operations available.
• Resolvers: Functions that resolve a query to the actual data. 📜 Example Query

query {
	user(id: '1') {
		name
		email
	}
}

🏗️ Setting up a GraphQL server

Using Apollo Server 🚀

1. Install apollo server:

npm install apollo-server graphql

2. Create a basic server:

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

// Define the schema
const typeDefs = gql`
  type Query {
    hello: String
  }
`;

// Define the resolvers
const resolvers = {
  Query: {
    hello: () => 'Hello world!',
  },
};

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

// Start the server
server.listen().then(({ url }) => {
  console.log(`🚀 Server ready at ${url}`);
});

🧩 Intermediate concepts

🔔 Subscriptions

Subscriptions allow clients to subscribe to real-time updates. Here’s a simple example:

type Subscription {
  messageAdded: Message
}

📱 Using Apollo Client

1. Install Apollo Client:

npm install @apollo/client graphql

2. Setup Apollo client

import { ApolloClient, InMemoryCache, gql } from '@apollo/client';

const client = new ApolloClient({
  uri: 'http://localhost:4000/',
  cache: new InMemoryCache(),
});

client
  .query({
    query: gql`
      query GetUsers {
        users {
          name
        }
      }
    `,
  })
  .then(result => console.log(result));

🧙‍♂️ Advanced Topics

🛡️ TypeScript and GraphQL

Using TypeScript with GraphQL ensures type safety. Here’s a basic setup:

1. Install Dependencies:

npm install @types/graphql graphql-codegen

2. Generate types:

graphql-codegen --config codegen.yml

⚡Optimizing Performance

• Batching: Use data loader to batch requests and reduce database calls.
• Caching: Implement caching strategies to improve performance.