TypeScript is a strongly typed superset of JavaScript that compiles to clean JavaScript output. GraphQL is a powerful query language for APIs that gives clients the power to request only the data they need from a server, making APIs more efficient.
The two technologies can be used together to create robust, type-safe API clients and servers. In this article, we'll look at how to use TypeScript with GraphQL, including a short code example.
There are several reasons you might want to use TypeScript with GraphQL. First, TypeScript can help you create type-safe GraphQL queries. This means that you can catch errors early, before your code even runs.
Second, TypeScript can provide autocompletion and type safety for your GraphQL server. This is especially useful when you're using a complex GraphQL schema with many types and fields.
Third, TypeScript can help you with code organization. For example, you can use TypeScript's module system to structure your code in a way that's easy to understand and maintain.
Fourth, TypeScript is becoming increasingly popular, and so using it with GraphQL can make it easier to find collaborators and support.
To use TypeScript with GraphQL, you'll need to install the following dependencies:
You can install these dependencies using npm:
npm install --save typescript graphql @types/graphql
Once you've installed the dependencies, you can start using TypeScript with GraphQL. Here's a simple example:
query GetUser($id: ID!) {
user(id: $id) {
id
name
}
}
In this example, we've defined a GraphQL query that fetches a user by their ID. We've also defined a type for the ID variable. This type will be used to type-check our query variables.
Now let's look at how to use this query with TypeScript. First, we'll need to create a file called schema.ts
:
import {
GraphQLSchema,
GraphQLObjectType,
GraphQLString,
GraphQLID,
} from 'graphql';
const UserType = new GraphQLObjectType({
name: 'User',
fields: {
id: { type: GraphQLID },
name: { type: GraphQLString },
},
});
const QueryType = new GraphQLObjectType({
name: 'Query',
fields: {
user: {
type: UserType,
args: {
id: { type: GraphQLID },
},
resolve: (_, { id }) => ({ id, name: 'Alice' }),
},
},
});
export const schema = new GraphQLSchema({
query: QueryType,
});
In this file, we've defined our GraphQL schema. We've also defined a User
type and a Query
type. The Query
type contains a user
field, which fetches a User
by their ID.
Now let's create a file called index.ts
:
import { graphql, buildSchema } from 'graphql';
import { schema } from './schema';
async function main() {
const query = `
query GetUser($id: ID!) {
user(id: $id) {
id
name
}
}
`;
const variables = {
id: '1',
};
const rootValue = {};
const context = {};
const options = {};
const result = await graphql(schema, query, rootValue, context, options);
console.log(result);
}
main();
In this file, we've imported the graphql
function from the graphql
package. We've also imported our schema
from the schema.ts
file.
Then we've defined a GraphQL query that fetches a user by their ID. We've also defined a variables
object, which contains the ID of the user we want to fetch.
Finally, we've called the graphql
function, passing in our schema
, query
, rootValue
, context
, and options
. This function will execute our query and return the result.
If we run this code, we'll get the following output:
{
"data": {
"user": {
"id": "1",
"name": "Alice"
}
}
}
As you can see, our query executed successfully and returned the data we requested.
In this article, we've looked at how to use TypeScript with GraphQL. We've seen how TypeScript can help you create type-safe GraphQL queries and how to use the graphql
function to execute those queries.