GraphQL.js

This is a technical preview of the JavaScript reference implementation for GraphQL, a query language created by Facebook for describing data requirements on complex application data models.

Technical Preview Contents

This technical preview contains a [draft specification for GraphQL] (https://github.com/facebook/graphql) and a reference implementation in JavaScript that implements that draft, GraphQL.js.

The reference implementation provides base libraries in JavaScript that would provide the basis for full GraphQL implementations and tools. It is not a fully standalone GraphQL server that a client developer could use to start manipulating and querying data. Most importantly, it provides no mapping to a functioning, production-ready backend. The only “backend” we have targeted for this early preview are in-memory stubs in test cases.

We are releasing this now because after GraphQL was first discussed publicly, many engineers used this information to implement the parts of the system that we discussed publicly. We want to support those engineers by providing both a formal specification and a reference implementation for the system as a whole.

To that end, the target audience is not the client developer, but those who have built or are actively interested in building their own GraphQL implementations and tools. Critically, we also want feedback on the system and to incorporate that feedback in our final release.

In order to be broadly adopted, GraphQL will have to target a wide variety of backends, frameworks, and languages, which will necessitate a collaborative effort across projects and organizations. This technical preview marks the beginning of that process.

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

npm install 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: () => 'world'
      }
    }
  })
});

This defines a simple schema with one type and one field, that resolves to a fixed value. 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);

});

Contributing

After cloning this repo, ensure dependencies are installed by running:

npm install

GraphQL is written in ES6 and uses Babel for ES5 transpilation and Flow for type safety. Widely consumable JavaScript can be produced by running:

npm run build

Once npm run build has run, you may import or require() directly from node.

After developing, the full test suite can be evaluated by running:

npm test

While actively developing, we recommend running

npm run watch

in a terminal. This will watch the file system run lint, tests, and type checking automatically whenever you save a js file.

To lint the JS files and type interface checks run npm run lint.