class EventSource

Supported only in the v8 engine. Introduced in Max v9.2.0.

A Server-Sent Events client.

URLs must be absolute http:// or https:// URLs. Successful connections require 200 OK and a content-type beginning with text/event-stream. On failure the client dispatches error and reconnects (default delay 3000 ms, overridable by the stream's retry: field).

Example

const source = new EventSource("http://127.0.0.1:8093/sse/basic");
source.onopen = () => post("sse open\n");
source.onmessage = (event) => {
  post(event.data, "\n");
  source.close();
};
source.onerror = () => post("sse error\n");

Index

Constructors

• new EventSource(url, options)

Properties

• CLOSED
• CONNECTING
• onerror
• onmessage
• onopen
• OPEN
• readyState
• url
• withCredentials

Methods

• addEventListener(type, listener)
• close()
• removeEventListener(type, listener)

new EventSource(url, options)

new EventSource(url: string, options?: { withCredentials?: boolean });

Constructs a new instance of the EventSource class

addEventListener(type, listener)

Registers a listener. Use a custom type to receive named event: messages from the stream.

addEventListener(
  type: string,
  listener: (event: EventSourceMessageEvent) => void,
): void;

close()

Closes the connection permanently (no reconnect).

close(): void;

CLOSED number read-only

Closed state constant.

CONNECTING number read-only

Connecting state constant.

onerror ((event: { type: string }) => void) | null

Called on error (before an automatic reconnect).

onmessage ((event: EventSourceMessageEvent) => void) | null

Called when a default (unnamed) message arrives.

onopen ((event: { type: string }) => void) | null

Called when the connection opens.

OPEN number read-only

Open state constant.

readyState number read-only

The connection state.

removeEventListener(type, listener)

Removes an event listener.

removeEventListener(
  type: string,
  listener: (event: EventSourceMessageEvent) => void,
): void;

url string read-only

The stream URL.

withCredentials boolean read-only

Whether cross-origin credentials are used.