GraphQL has become a popular choice for building APIs due to its flexibility and efficiency. One key aspect of GraphQL is mutations, which allow us to modify data on the server side. In this tutorial, we will walk through the process of implementing mutations in a JavaScript application.

Setup

Before getting started, make sure you have a GraphQL server set up. You can use popular GraphQL server libraries like Apollo Server or Express-GraphQL to create a server.

Once you have your server up and running, you can follow the steps below to implement mutations.

Writing the Mutation

1. Define your mutation schema: In GraphQL, you define mutations in your schema just like you would define queries. Start by declaring a mutation type and define the fields for your mutation.

type Mutation {
  createUser(name: String!, email: String!): User!
}

In the above example, we are creating a createUser mutation that takes in name and email as required arguments and returns a User object.

1. Implement the resolver: Resolvers are functions that resolve the incoming requests for a particular field. In the case of a mutation, the resolver will handle the creation of a new user.

const resolvers = {
  Mutation: {
    createUser: (parent, args) => {
      // Logic to create a new user
      // args.name - user name
      // args.email - user email

      // In this example, we will simply return the created user object
      const newUser = {
        id: '1',
        name: args.name,
        email: args.email
      };

      return newUser;
    }
  }
};

The above code shows a simple implementation of the resolver for the createUser mutation. You can add your own business logic for creating a user in your application.

Calling the Mutation

1. Install a GraphQL client library: To call the mutation from your JavaScript application, you will need a GraphQL client library. Popular choices include Apollo Client for React applications and Apollo Boost for vanilla JavaScript or Node.js applications.

2. Create a GraphQL client: Instantiate the GraphQL client with your server’s endpoint and any required configurations.

import ApolloClient from 'apollo-boost';

const client = new ApolloClient({
  uri: 'http://your-graphql-server-endpoint',
  // Other configuration options
});

1. Call the mutation using the GraphQL client: Use the mutate method of the client to execute the mutation.

client.mutate({
  mutation: gql`
    mutation CreateUser($name: String!, $email: String!) {
      createUser(name: $name, email: $email) {
        id
        name
        email
      }
    }
  `,
  variables: {
    name: 'John Doe',
    email: 'john@example.com'
  }
})
  .then(response => {
    // Handle the response
    console.log(response.data.createUser);
  })
  .catch(error => {
    // Handle any errors
    console.error(error);
  });

In the above code, we are using the gql helper from the GraphQL client library to write our mutation query. The variables object is used to pass the values for name and email.

That’s it! You have successfully implemented a GraphQL mutation in JavaScript. You can extend this example to handle more complex mutations and build powerful APIs using GraphQL.

#javascript #GraphQL #mutations