SSE-Z

> A slim, easy-to-use wrapper around SSE.

Installation

``
npm install sse-z
`

Usage

`ts
import { SSESubscription } from "sse-z";

const subscription = new SSESubscription({
url: "http://localhost:8080/sse",
searchParams: {
foo: "bar",
},
onNext: (type: string, data: string) => {
console.log(type, data);
},
});

// stop the subscription
subscription.unsubscribe();
`

Types

`ts
class SSESubscription {
eventSource: EventSource;

constructor(options: SSESubscriptionOptions);

unsubscribe(): void;
}

interface SSESubscriptionOptions {
// Additional options to pass to the constructor of the underlying EventSource instance.
eventSourceOptions?: {
withCredentials?: boolean;
[key: string]: any;
};

// Indicates the subscription should expect keep alive events to be sent by the server.
// If an event is not received inside the provided interval, a reconnection attempt will be made.
// The provided interval should be greater than the actual frequency at which the server sends
// the events to allow for network latency.
keepAlive?: {
// Defaults to "keepAlive";
eventType?: string;
intervalMs: number;
};

// Called when the connection is terminated by calling unsubscribe.
onComplete?: () => void;

// Called when an error occurs. Note that this callback will be called each time the connection
// is lost, so it should not be used to indicate a critical error occurred.
onError?: (error: Error) => void;

// Callback called whenever an event is pushed.
onNext?: (type: string, data: string) => void;

// Any URL query parameters to attach to the URL.
searchParams?: {
[key: string]: string;
};

// The URL of the endpoint to fetch requests from.
url: string;
}
`

$3

#### Relay

`ts
import {
Environment,
Network,
Observable,
SubscribeFunction,
} from "relay-runtime";
import { SSESubscription } from "sse-z";

const subscribe: SubscribeFunction = (operation, variables) => {
return Observable.create((sink) => {
return new SSESubscription({
url: 'http://localhost:8080/graphql',
searchParams: {
operationName: operation.name,
query: operation.text,
variables: JSON.stringify(variables),
},
eventSourceOptions: {
// Ensure cookies are included with the request
withCredentials: true,
},
onNext: (type, data) => {
// Note: the actual type may vary by server
if (type === 'event') {
sink.next(JSON.parse(data));
}
},
});
});
};

const environment = new Environment({
...
network: Network.create(fetchQuery, subscribe),
});
`

#### Apollo Client

`ts
import { ApolloLink, Operation, FetchResult, Observable } from "@apollo/client";
import { print } from "graphql";
import { SSESubscription, SSESubscriptionOptions } from "sse-z";

class SSELink extends ApolloLink {
options: SSESubscriptionOptions;

constructor(options: SSESubscriptionOptions) {
super();
this.options = options;
}

public request({
query,
variables,
operationName,
}: Operation): Observable {
return new Observable((sink) => {
const subscription = new SSESubscription({
...options,
searchParams: {
query: print(operation.query),
variables: JSON.stringify(variables),
operationName,
},
onNext: (type, data) => {
// Note: the actual type may vary by server
if (type === "event") {
sink.next(JSON.parse(data));
}
},
});

return () => subscription.unsubscribe();
});
}
}

const link = new SSELink({
url: "http://localhost:8080/graphql",
eventSourceOptions: {
// Ensure cookies are included with the request
withCredentials: true,
},
});
``