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The MessagePort interface of the Channel Messaging API represents one of the two ports of a MessageChannel, allowing sending of messages from one port and listening out for them arriving at the other.

Note: 此特性在 Web Worker 中可用。

Methods

Inherits methods from its parent, EventTarget

MessagePort.postMessage
Sends a message from the port, and optionally, transfers ownership of objects to other browsing contexts.
MessagePort.start
Starts the sending of messages queued on the port (only needed when using EventTarget.addEventListener; it is implied when using MessagePort.onmessage.)
MessagePort.close
Disconnects the port, so it is no longer active.

Event handlers

Inherits event handlers from its parent, EventTarget

MessagePort.onmessage
Is an EventListener that is called whenever an MessageEvent of type message is fired on the port — that is, when the port receives a message.

Example

In the following code block, you can see a new channel being created using the MessageChannel.MessageChannel constructor. When the IFrame has loaded, we transfer MessageChannel.port2 (a MessagePort) to the IFrame using MessagePort.postMessage along with a message. The handleMessage handler then responds to a message being sent back from the IFrame (using MessagePort.onmessage), putting it into a paragraph.

var channel = new MessageChannel();
var para = document.querySelector('p');
    
var ifr = document.querySelector('iframe');
var otherWindow = ifr.contentWindow;

ifr.addEventListener("load", iframeLoaded, false);
    
function iframeLoaded() {
  otherWindow.postMessage('Hello from the main page!', '*', [channel.port2]);
}

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

For a full working example, see our channel messaging basic demo on Github (run it live too).

Specifications

Specification Status Comment
HTML Living Standard
MessagePort
Living Standard No difference from Unknown.
Unknown
MessagePort
Unknown W3C version of the spec

Browser compatibility

We're converting our compatibility data into a machine-readable JSON format. This compatibility table still uses the old format, because we haven't yet converted the data it contains. Find out how you can help!

Feature Chrome Edge Firefox (Gecko) Internet Explorer Opera Safari (WebKit)
Basic support 4 (Yes) 未实现 10.0 10.6 5
Available in workers (Yes) ? 41 (41) (Yes) (Yes) (Yes)
Feature Android Chrome for Android Edge Firefox Mobile (Gecko) Firefox OS (Gecko) IE Phone Opera Mobile Safari Mobile
Basic support 4.4 4 (Yes) 未实现 未实现 10.0 11.5 5.1
Available in workers (Yes) (Yes) ? 41.0 (41) (Yes) (Yes) (Yes) (Yes)

See also

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