This is an experimental technology
Because this technology's specification has not stabilized, check the compatibility table for usage in various browsers. Also note that the syntax and behavior of an experimental technology is subject to change in future versions of browsers as the specification changes.
The Client.postMessage() method of the Client interface allows a service worker client to send a message to a ServiceWorker.
Note: Messages sent to service worker contexts (e.g. as the event object of onmessage are represented by MessageEvent objects in modern browsers, for consistency with other web messaging features. (They used to be represented by ServiceWorkerMessageEvent objects, which have now been deprecated.)
Syntax
Client.postMessage(message[, transfer]);
Returns
Void.
Parameters
message- The message to send to the service worker.
transfer Optional- A transferable object such as, for example, a reference to a port.
Examples
This code snippet is taken from the service worker post-message sample (see post-message live.) The code sends message data and transfers the port to the service worker so that it can reply via Client.postMessage().
The message is wrapped in a promise that resolves if the response doesn't contain an error and rejects with the error.
function sendMessage(message) {
return new Promise(function(resolve, reject) {
var messageChannel = new MessageChannel();
messageChannel.port1.onmessage = function(event) {
if (event.data.error) {
reject(event.data.error);
} else {
resolve(event.data);
}
};
navigator.serviceWorker.controller.postMessage(message, [messageChannel.port2]);
});
}
Specifications
| Specification | Status | Comment |
|---|---|---|
| Service Workers The definition of 'postMessage()' in that specification. |
Working Draft | Initial definition. |
Browser compatibility
| Feature | Chrome | Firefox (Gecko) | Internet Explorer | Opera | Safari (WebKit) |
|---|---|---|---|---|---|
| Basic support | 45.0[1] | 44.0 (44.0)[2] | No support | ? | No support |
| Feature | Android | Android Webview | Firefox Mobile (Gecko) | Firefox OS | IE Mobile | Opera Mobile | Safari Mobile | Chrome for Android |
|---|---|---|---|---|---|---|---|---|
| Basic support | No support | No support | 44.0 (44.0) | ? | No support | ? | No support | 45.0 [1] |
- [1] Behind a flag in Chrome 40 through 44.
- [2] Service workers (and Push) have been disabled in the Firefox 45 & 52 Extended Support Releases (ESR.)