What is GraphQL?

Before we start learning how to use GraphQL, let’s first focus on what GraphQL is. Like REST, it is a way to query APIs. However, it is also much more than that. GraphQL includes a server-side runtime for executing queries and a type system to define your data. It works with many database engines and can be integrated into your existing backend.

GraphQL services are created by defining types (such as a User type), fields on types (such as a username field), and functions to resolve values of fields. Let’s assume we have defined the following User type with a function to get a username:

type User {
  username: String
}
function User_username(user) {
  return user.getUsername()
}

We could then define a Query type and a function to get the current user:

type Query {
  currentUser: User
}
function Query_currentUser(req) {
  return req.auth.user
}

Info

The Query type is a special type that defines the...