MessagePort.onmessage

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 MessagePort 接口的 onmessage 事件处理程序是一个EventListener, 当在端口上触发一个类型为 messageMessageEvent 时被调用 - 即,当端口接收到消息时。

Note: This feature is available in Web Workers.

Syntax

channel.onmessage = function() { ... };

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 pass MessageChannel.port2 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 onmessage, putting it into a paragraph — MessageChannel.port1 is listened to, to check when the message arrives.

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
WHATWG HTML Living Standard
onmessage
Living Standard No difference from HTML5 Web Messaging.
HTML5 Web Messaging
onmessage
Recommendation W3C version of the spec

Browser compatibility

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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