MessagePort: start() method

Baseline Widely available

This feature is well established and works across many devices and browser versions. It’s been available across browsers since September 2015.

Note: This feature is available in Web Workers.

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 onmessage.

Syntax

start()

Parameters

None.

Return value

None (undefined).

Examples

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

js
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:

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

channel.port1.start();