GraphQL Installation

Let's start with GraphQL.js installation. You must have the following things before going to start.

• We need a computer system with running Windows, Linux, or macOS operating system. Here, we are using Windows.
• We need the latest version of a web browser. Here, we recommend Google Chrome.
• Install the latest version of Node.js. See how to install node.js: https://www.javatpoint.com/install-nodejs or go to node.js official website https://nodejs.org/en/ and download and install the latest version of node.js

There are two ways to execute GraphQL queries:

• Execute GraphQL query with a command-line tool
• Run an Express GraphQL Server to execute query

Execute GraphQL query with a command-line tool

Here, we are not using any language features that require transpilation, but we will use some ES6 features like Promises, classes, and fat arrow functions, etc.

• Open node.js command prompt.
• Run the following command to create a new project and install GraphQL.js.

How to write the code?

There are three important components for GraphQL application. i.e. schema, query, and resolver. When we write a query for the GraphQL server, then to handle GraphQL queries, we need a schema. The schema is used to define the Query type. We also require an API root with a function called a "resolver" for each API endpoint.

Let's make an API to simple return "Hello World". Create a server.js file in the current folder where node.js is installed and write the following code:

Now, run this using the following command:

Here, you can see the GraphQL response printed as

This is a simple GraphQL query that you executed on command prompt without using a server.

Run an Express GraphQL Server to execute query

The easiest way to run a GraphQL API server is to use Express. Express is a popular web application framework for Node.js.

If you have not installed Express yet, first install Express by using the following command

See this link for more information: https://www.javatpoint.com/install-expressjs

You have to install two additional dependencies by using the following command:

How to write the code?

Modify the "server.js" file with the following code to make an API server rather than a script that runs a single query. Here, we use the 'express' module to run a webserver, and instead of executing a query directly with the graphql function, we can use the express-graphql library to mount a GraphQL API server on the "/graphql" HTTP endpoint

Now, run the GraphQL server by using the following command:

The GraphQL API server is running now. Open https://localhost:4000/graphql on a web browser.

Here, you can see that how to run a GraphQL server and how to use the GraphiQL interface to issue queries. Next TopicGraphQL Architecture