---
title: "Building a GraphQL API in JavaScript"
description: "GraphQL lets API clients specify the fields they need instead of accepting a server-defined response, reducing unnecessary payload and potentially combining data from multiple stores behind one endpoint. The tutorial builds a JavaScript/Node.js implementation by loading Schema Definition Language (SDL) with graphql-tools, defining Query, User, and Address types, and connecting fields to resolver functions. Resolvers receive field arguments and can use context for authorization, illustrated by restricting address access to the current user. It also recommends keeping business logic separate from resolvers and notes that GraphQL does not eliminate database performance, caching, logging, monitoring, or versioning concerns. The discussion presents GraphQL as useful for evolving, front-end-heavy applications, while warning that its single HTTP status code and schema versioning limitations can complicate error handling and breaking changes."
---

# Building a GraphQL API in JavaScript

[Heroku](https://yomu.fyi/company/heroku) · Owen Ou · Jun 24, 2020

**Type:** Tutorial

## Summary

GraphQL lets API clients specify the fields they need instead of accepting a server-defined response, reducing unnecessary payload and potentially combining data from multiple stores behind one endpoint. The tutorial builds a JavaScript/Node.js implementation by loading Schema Definition Language (SDL) with graphql-tools, defining Query, User, and Address types, and connecting fields to resolver functions. Resolvers receive field arguments and can use context for authorization, illustrated by restricting address access to the current user. It also recommends keeping business logic separate from resolvers and notes that GraphQL does not eliminate database performance, caching, logging, monitoring, or versioning concerns. The discussion presents GraphQL as useful for evolving, front-end-heavy applications, while warning that its single HTTP status code and schema versioning limitations can complicate error handling and breaking changes.

## Context

The post addresses the need for clients to fetch only the data they require, reduce payloads and network calls, and handle data that may come from multiple stores. It also considers GraphQL’s trade-offs, including authorization, error handling, performance, and schema versioning.

## Approach / What changed

It defines a GraphQL schema in SDL for Query, User, and Address types, loads it with graphql-tools in Node.js, and implements field resolvers over dummy user data. Resolver context is used to restrict access to sensitive address information, while broader guidance separates business logic from resolver logic.

## Takeaways

- GraphQL queries let clients select specific fields and can combine related data through a single endpoint rather than several REST calls.
- SDL defines GraphQL objects, fields, argument types, and the Query entry point; resolvers provide the underlying field values.
- Authorization can be enforced in a field resolver using context, while GraphQL’s single HTTP status code and limited versioning guidance complicate error handling and breaking changes.

**Tags:** [API](https://yomu.fyi/topic/api), [GraphQL](https://yomu.fyi/topic/graphql), [JavaScript](https://yomu.fyi/topic/javascript), [Node.js](https://yomu.fyi/topic/node-js)

- Source: [Heroku](https://www.heroku.com/blog/building-graphql-api-javascript)
- Source URL: https://www.heroku.com/blog/building-graphql-api-javascript
- Ingested by Yomu: 2026-09-09T16:04:45.990Z

[Read original post](https://www.heroku.com/blog/building-graphql-api-javascript)