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Building a GraphQL Endpoint with Deno

Queries and Mutations

Explore how to define and implement basic GraphQL queries and mutations in a Deno application. Learn to handle data retrieval and additions for books, authors, and reviews while testing operations using a GraphiQL interface. Understand schema definitions, resolver setup, and running a Deno server to serve your GraphQL endpoint.

We'll cover the following...

Overview

Now that we have defined the schema, types, queries, and mutations, let’s dive deeper into these concepts. To keep everything simple, we’ll define the following queries:

  • getAllBooks()
  • getAllAuthors()
  • getBook(id: String)
  • getAuthor(id: String)

We’ll also define the following mutations:

  • addBook(input: BookInput!)
  • addAuthor(input: AuthorInput!)
  • addReview(input: ReviewInput!)

Note: We’ll only add the entities for now and we won’t link them (that is, we won’t add an author and reviews to a book).

Queries

Now that we’ve listed our queries, let’s start defining them. First of all, we need some data, so let’s add the following example data:

TypeScript 3.3.4
// Books data
const books = [
    {
        id: "1",
        title: "Eloquent JavaScript, Third Edition",
        price: 32.23,
        identifier: "9781593279509",
        description: "JavaScript lies at the heart of almost every modern web application, from social apps like Twitter to browser-based game frameworks like Phaser and Babylon. Though simple for beginners to pick up and play with, JavaScript is a flexible, complex language that you can use to build full-scale applications."
    },
    {
        id: "2",
        title: "Practical Modern JavaScript",
        price: 30.49,
        identifier: "9781491943533",
        description: "To get the most out of modern JavaScript, you need to learn the latest features of its parent specification, ECMAScript 6 (ES6). This book provides a highly practical look at ES6, without getting lost in the specification or its implementation details."
    },
    {
        id: "3",
        title: "Understanding ECMAScript 6",
        price: 25.50,
        identifier: "9781593277574",
        description: "ECMAScript 6 represents the biggest update to the core of JavaScript in the history of the language. In Understanding ECMAScript 6, expert developer Nicholas C. Zakas provides a complete guide to the object types, syntax, and other exciting changes that ECMAScript 6 brings to JavaScript."
    }
];
// Authors data
const authors = [
    {
        id: "1",
        firstName: "Marijn",
        lastName: "Haverbeke"
    },
    {
        id: "2",
        firstName: "Nicolás",
        lastName: "Bevacqua"
    },
    {
        id: "3",
        firstName: "Nicholas",
        lastName: "Zakas"
    }
];
// Reviews data
const reviews = [];

Now let’s define our queries below:

TypeScript 3.3.4
const resolvers = {
    Query: {
        getAllBooks: () => {
            return books;
        },
        getAllAuthors: () => {
            return authors
        },
        getBook: (_parent: any, { id }: { id: string }) => {
            console.log(`getBook() id=(${id})`);
            return books.find((book) => book.id === id);
        },
        getAuthor: (_parent: any, { id }: { id: string }) => {
            console.log(`getAuthor() id=(${id})`);
            return authors.find((author) => author.id === id);
        }
    }
};

We can use the code widget below to test our queries. Try using one of the queries we defined in a new ...