The onconnect property of the SharedWorkerGlobalScope interface is an event handler representing the code to be called when the connect event is raised — that is, when a MessagePort connection is opened between the associated SharedWorker and the main thread.


onconnect = function() { ... };


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.

onconnect = function(e) {
    var port = e.ports[0];

    port.onmessage = function(e) {
      var workerResult = 'Result: ' + ([0] *[1]);


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

Note: The data property of the event object used to be null in Firefox. As of version 65 it is now initialized to an empty string, as per spec (bug 1508824).


HTML Standard (HTML)
# handler-sharedworkerglobalscope-onconnect

Browser compatibility

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See also