jetblack-graphql-client

This is work in progress.

Overview

A simple non-caching GraphQL client for query, mutation and subscription.

I wanted a simple non-caching GraphQL subscription client written in ES6 javascript with no external dependencies.

The protocol for GraphQL WebSocket subscriptions can be found here.

This implementation is deliberately explicit and low on features as I wanted to keep the algorithm clear. Features like observables and caching should be implmented in other libraries. For example see here for a reconnecting subscriber.

Installation

Install from npm.

yarn add @jetblack/graphql-client

Usage

There are two functions:

graphQLSubscriber (url, options, callback, protocols = 'graphql-ws')
graphQLFetch (url, query, variables = {}, operationName = null, init = fetchOptions)

The graphQLSubscriber implements the WebSocket protocol. The function takes the url for the WebSocket, an options object which is simply passed as JSON to the server, and a callback with the prototype (error, subscribe). A function is returned which can be used to shutdown the subscriber. If both error and subscribe are null the connection has been closed normally.

The subscribe argument is a function with the prototype subscribe(query, variables, operationName, callback). When subscribe is called it returns a function that can be called to unsubscribe. The callback to the subscribe function has the prototype callback(error, data). If both error and data are null then connection hs been closed normally.

The protocols defaults to "graphql-ws". The documentation suggests this can be an array or strings, but the first should be the default.

The graphQLFetch function is a simple fetch implementation for query and mutation operations. There are numerous implementations of this available, and it is provided for convenience. The init parameter is passed through to fetch. It has the default value fetchOptions which is defined as:

const fetchOptions = {
  method: 'post',
  headers: { 'Content-Type': 'application/json' }
}

// The fetchOptions can be extended.
const myFetchOptions = {
    ...fetchOptions,
    mode: 'cors'
}

There follows an example of the graphQLSubscriber.

import { Subscriber } from '@jetblack/graphql-client'

const url = 'ws://localhost/subscriptions'
const options = {}

const query = `
subscription {
    mySubscription {
        someData
    }
}
`
variables = {}
operationName = null

const shutdown = graphQLSubscriber(
    url,
    options,
    (error, subscribe) => {
        if (!(error || subscribe)) {
            // Normal closure.
            return
        }
        if (error) {
            console.error(error)
            throw error
        }
        const unsubscribe = subscribe(
            query,
            variables,
            operationName,
            (error, data) => {
                if (!(error || subscribe)) {
                    // Normal closure
                    return
                }
                if (error) {
                    console.error(error)
                    throw error
                }
                console.log(data)
            })
        
        // Some time later ...
        unsubscribe()
    })

// Some time later ...
shutdown()

The graphQLFetch function is used as follows.

import { Fetcher } from '@jetblack/graphql-client'

const fetcher = new RetryFetcher('http://localhost/graphql')

// An example mutation.
graphQLFetch(
    `
mutate CreditAccount($account: ID!, $amount: Float!) {
    creditAccount(account: $account, amount: $amount) {
        balance
    }
}`,
    {
        account: '1234',
        amount: 19.99
    }
)
.then(respoonse => response.json())
.then(response => {
    console.log(response.data.balance)
})
.catch(error => {
    console.error(error)
})

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