SharedWorkerGlobalScope: connect event

The connect event is fired in shared workers at their SharedWorkerGlobalScope when a new client connects.

This event is not cancelable and does not bubble.


Use the event name in methods like addEventListener(), or set an event handler property.

addEventListener("connect", (event) => {});

onconnect = (event) => {};

Event type

Event properties

This interface also inherits properties from its parent, Event. Read only

The data sent by the message emitter.

MessageEvent.origin Read only

A string representing the origin of the message emitter.

MessageEvent.lastEventId Read only

A string representing a unique ID for the event.

MessageEvent.source Read only

A MessageEventSource (which can be a WindowProxy, MessagePort, or ServiceWorker object) representing the message emitter.

MessageEvent.ports Read only

An array of MessagePort objects representing the ports associated with the channel the message is being sent through (where appropriate, e.g. in channel messaging or when sending a message to a shared worker).


This example shows a shared worker file — when a connection to the worker occurs from a main thread via a MessagePort, the onconnect event handler fires. The event object is a MessageEvent.

The connecting port can be referenced through the event object's ports parameter; this reference can have an onmessage handler attached to it to handle messages coming in through the port, and its postMessage() method can be used to send messages back to the main thread using the worker.

self.onconnect = (e) => {
  const port = e.ports[0];

  port.onmessage = (e) => {
    const workerResult = `Result: ${[0] *[1]}`;


For a complete running example, see our Basic shared worker example (run shared worker.)

addEventListener equivalent

You could also set up an event handler using the addEventListener() method:

self.addEventListener("connect", (e) => {
  const port = e.ports[0];

  port.onmessage = (e) => {
    const workerResult = `Result: ${[0] *[1]}`;


HTML Standard
# event-workerglobalscope-connect
HTML Standard
# handler-sharedworkerglobalscope-onconnect

Browser compatibility

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See also