Unlock the Power of TypeScript and GraphQL: A Comprehensive Guide
Why Choose TypeScript with GraphQL?
When building robust APIs, it’s essential to ensure seamless communication between the frontend and backend. GraphQL, a query language for APIs, helps prevent over and under-fetching of data by using its type system to describe data fields. However, GraphQL operates with two core components: Schema objects and resolvers. The Schema objects define what properties can be queried in the API, but the resolvers do not understand the Schema types. This is where TypeScript comes in – by using TypeScript, which compiles to JavaScript, we can define types for our resolvers that match our Schema, preventing mismatches.
Introducing TypeGraphQL: Simplifying GraphQL API Creation
TypeGraphQL, a library that simplifies the process of creating GraphQL APIs in Node.js, automatically creates GraphQL schema definitions from TypeScript classes with decorators. This means we only need to define the resolver types, and our GraphQL schema will be generated. TypeGraphQL includes advanced features like automatic validation, dependency injection, authorization, and inheritance, allowing us to define our GraphQL schema types and interfaces using TypeScript classes and decorators.
Getting Started with TypeGraphQL and TypeScript
To follow along with this tutorial, you’ll need familiarity with TypeScript and GraphQL, Node.js installed on your machine, and TypeScript installed globally on your machine. You can access the full code for this tutorial on the GitHub repo.
Bootstrapping Our TypeScript + GraphQL Application
First, let’s create a new directory and name it. We can then initialize a new package.json file with the npm init command. Next, we’ll install our project dependencies, including TypeGraphQL, apollo-server-express, class-validator, and mongoose.
Setting Up Our Apollo Server
Now that we have installed our dependencies, we’ll set up our Apollo Server with the apollo-server-express package. We’ll create a new app directory in our project directory and set up our server.ts file to import reflect-metadata and type-graphql.
TypeGraphQL Database Schema Fields
The content inside our schema.gql file is based on the schema fields for our different database entities, stored in the entities folder. We’ll use the ObjectType decorator to mark the class as the GraphQLObjectType from graphql-js, and the Field decorator to declare the class properties that should be mapped to the GraphQL fields.
TypeGraphQL Resolvers and Input Types
Next, we’ll create a new folder called resolver, which will contain another folder called types. In types, we’ll add the types for our different resolver inputs. The input types define the data required to create entries for GraphQL mutations.
Running Our Apollo Application
To start our application, we’ll run npm run build-ts, which compiles our code, then npm start, which starts our server. We can then navigate to the GraphQL Playground at http://localhost:3333/graphql to test our API.
Exploring Advanced GraphQL Features
GraphQL aliases allow us to rename keys of the data returned in our API query result. For example, we can rename our result key from returnAllProduct to products using aliases. Additionally, GraphQL provides two built-in scalars for date: “timestamp” or “isoDate”.
The Power of TypeGraphQL and TypeScript
TypeGraphQL has led to the creation of tools and libraries that make it easier and faster to write applications that meet our expectations. By combining both TypeScript features and the benefits of GraphQL with the TypeGraphQL library, we can build resilient and strongly typed APIs that fulfill our needs in terms of maintenance, technical debt down the line, and more.
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