graphql

What is graphql?

The graphql npm package is the JavaScript reference implementation for GraphQL, a query language for APIs and a runtime for executing those queries by using a type system you define for your data. It allows you to create schemas, define resolvers, and execute GraphQL queries and mutations.

What are graphql's main functionalities?

Creating a GraphQL Schema

This feature allows you to define the shape of your data and the way it can be queried by clients. The code sample demonstrates how to create a simple GraphQL schema with a single root query.

const { GraphQLSchema, GraphQLObjectType, GraphQLString } = require('graphql');

const schema = new GraphQLSchema({
  query: new GraphQLObjectType({
    name: 'RootQueryType',
    fields: {
      hello: {
        type: GraphQLString,
        resolve() {
          return 'Hello world!';
        }
      }
    }
  })
});

Executing a GraphQL Query

This feature allows you to execute GraphQL queries against your schema. The code sample shows how to execute a simple query that asks for the 'hello' field, which resolves to 'Hello world!'.

const { graphql, buildSchema } = require('graphql');

const schema = buildSchema(`
  type Query {
    hello: String
  }
`);

const root = { hello: () => 'Hello world!' };

graphql(schema, '{ hello }', root).then((response) => {
  console.log(response);
});

Defining Resolvers

Resolvers are functions that resolve the value for a type or field in a schema. The code sample shows how to define a resolver for the 'hello' field that returns a string.

const { GraphQLObjectType, GraphQLString } = require('graphql');

const RootQueryType = new GraphQLObjectType({
  name: 'RootQuery',
  fields: {
    hello: {
      type: GraphQLString,
      resolve() {
        return 'Hello world!';
      }
    }
  }
});

Other packages similar to graphql

apollo-server

Apollo Server is a community-driven, open-source GraphQL server that works with many Node.js HTTP server frameworks. It simplifies building a GraphQL API by providing features like performance tracing and schema stitching. Compared to graphql, Apollo Server offers a more integrated set of tools for building production-ready GraphQL services.

express-graphql

Express GraphQL is a GraphQL HTTP server middleware for Express.js. It allows you to serve a GraphQL API as a web service. While graphql provides the core functionality for schema creation and query execution, express-graphql makes it easy to integrate GraphQL with the Express web application framework.

type-graphql

TypeGraphQL is a framework for building GraphQL APIs in Node.js using TypeScript, based on the official graphql-js package. It allows for defining the schema using TypeScript classes and decorators, which can be more familiar to developers with an object-oriented background. It provides a more type-safe and class-based approach to defining GraphQL schemas compared to the more traditional, function-based approach of graphql.

README

GraphQL.js

The JavaScript reference implementation for GraphQL, a query language for APIs created by Facebook.

See more complete documentation at http://graphql.org/ and http://graphql.org/graphql-js/.

Looking for help? Find resources from the community.

Getting Started

An overview of GraphQL in general is available in the README for the Specification for GraphQL. That overview describes a simple set of GraphQL examples that exist as tests in this repository. A good way to get started with this repository is to walk through that README and the corresponding tests in parallel.

Using GraphQL.js

Install GraphQL.js from npm

With yarn:

yarn add graphql

or alternatively using npm:

npm install --save graphql

GraphQL.js provides two important capabilities: building a type schema, and serving queries against that type schema.

First, build a GraphQL type schema which maps to your code base.

import {
  graphql,
  GraphQLSchema,
  GraphQLObjectType,
  GraphQLString
} from 'graphql';

var schema = new GraphQLSchema({
  query: new GraphQLObjectType({
    name: 'RootQueryType',
    fields: {
      hello: {
        type: GraphQLString,
        resolve() {
          return 'world';
        }
      }
    }
  })
});

This defines a simple schema with one type and one field, that resolves to a fixed value. The resolve function can return a value, a promise, or an array of promises. A more complex example is included in the top level tests directory.

Then, serve the result of a query against that type schema.

var query = '{ hello }';

graphql(schema, query).then(result => {

  // Prints
  // {
  //   data: { hello: "world" }
  // }
  console.log(result);

});

This runs a query fetching the one field defined. The graphql function will first ensure the query is syntactically and semantically valid before executing it, reporting errors otherwise.

var query = '{ boyhowdy }';

graphql(schema, query).then(result => {

  // Prints
  // {
  //   errors: [
  //     { message: 'Cannot query field boyhowdy on RootQueryType',
  //       locations: [ { line: 1, column: 3 } ] }
  //   ]
  // }
  console.log(result);

});

Want to ride the bleeding edge?

The npm branch in this repository is automatically maintained to be the last commit to master to pass all tests, in the same form found on npm. It is recommended to use builds deployed to npm for many reasons, but if you want to use the latest not-yet-released version of graphql-js, you can do so by depending directly on this branch:

npm install graphql@git://github.com/graphql/graphql-js.git#npm

Contributing

We actively welcome pull requests, learn how to contribute.

Changelog

Changes are tracked as GitHub releases.

License

GraphQL.js is MIT-licensed.