MessagePort.start

The start() method of the MessagePort interface starts the sending of messages queued on the port. This method is only needed when using EventTarget.addEventListener; it is implied when using MessageChannel.onmessage.

Syntax

port.start()

Returns

Void.

Parameters

None.

Example

In the following code block, you can see a handleMessage handler function, run when a message is sent back to this document using onmessage:

channel.port1.onmessage = handleMessage;
function handleMessage(e) {
  para.innerHTML = e.data;
}   

Another option would be to do this using EventTarget.addEventListener, however, when this method is used, you need to explicitly call start() to begin the flow of messages to this document:

channel.port1.addEventListener('message', handleMessage, false);
function handleMessage(e) {
  para.innerHTML = e.data;
  textInput.value = '';
}

channel.port1.start();

Specifications

Specification	Status	Comment
WHATWG HTML Living Standard The definition of 'start()' in that specification.	Living Standard	No difference from HTML5 Web Messaging.
HTML5 Web Messaging The definition of 'start()' in that specification.	Recommendation	W3C version of the spec

Browser compatibility

See also

• Using channel messaging