GraphQL is a query language for APIs and provides an efficient description of the data in your API. It also allows clients to specify exactly what data they need. This achievement is possible thanks to its structure and set of functionalities.
Here are the basic steps on how to use GraphQL with JavaScript:
1. Setting up your project:
First, initialize a new Node.js project and install the necessary dependencies, like `express`, `express-graphql`, and `graphql`. \`\`\`bash npm init npm i express express-graphql graphql \`\`\`1. Understanding the GraphQL Schema:
A GraphQL Schema defines the capabilities of a GraphQL API. It lays out the types of data provided, their fields, and the relationships between types.1. Building the GraphQL Schema:
\`\`\`javascript const { buildSchema } = require(‘graphql’); const schema = buildSchema(\` type User { id: ID name: String age: Int } type Query { user(id: ID!): User } \`); \`\`\` In the schema, we’ve defined a User type and a Query type. The Query type is a special type that lets us query the data.1. Build the Root Resolver
The root resolver implements the Query. Each field in a GraphQL type has a resolver function. \`\`\`javascript const root = { user: ({ id }) => { return getUser(id); // Assuming getUser is a function that returns user data from DataBase. }, }; \`\`\`1. Setting Up express-graphql Server
At last, set up an Express server that uses the `express-graphql` middleware: \`\`\`javascript const express = require(‘express’); const { graphqlHTTP } = require(‘express-graphql’); const app = express(); app.use( “/graphql”, graphqlHTTP({ schema: schema, rootValue: root, graphiql: true, // Enable GraphiQL interactive in-browser GraphQL IDE }), ); app.listen(4000); \`\`\`1. Querying from the client-side
After starting the server, open your browser and browse `http://localhost:4000/graphql`, then you can write and test your queries here. For example, to fetch a user you would use: \`\`\`graphql { user(id: “1”) { name, age } } \`\`\` 1. Setting Up Apollo Client (Optional) Apollo Client is a comprehensive state management library for JavaScript that enables you to manage both local and remote data with GraphQL. You can use it to fetch, cache, and modify application data, all while automatically updating your UI. Install it using npm: \`\`\`bash npm install @apollo/client graphql \`\`\` Then wrap your application with `ApolloProvider` and pass the client instance into the `client` prop. Then you can use Apollo Client’s hooks for executing queries like `useQuery`.Note: The examples provided consider a very basic usage of GraphQL. For large scale application with GraphQL, you would usually have a database where you store data, you would also handle mutations (modify data: create, update, delete), and would likely split your schema and resolver definitions into multiple files.
