Fired when a message is sent from either an extension process or a content script.
Syntax
browser.runtime.onMessage.addListener(function(
message, // optional any
sender, // MessageSender
function() {...} // function
) {...})
browser.runtime.onMessage.removeListener(listener)
browser.runtime.onMessage.hasListener(listener)
Events have three functions:
addListener(callback)- Adds a listener to this event.
removeListener(listener)- Stop listening to this event. The
listenerargument is the listener to remove. hasListener(listener)- Check whether
listeneris registered for this event. Returnstrueif it is listening,falseotherwise.
addListener syntax
Parameters
callback-
Function that will be called when this event occurs. The function will be passed the following arguments:
messageany. The message sent by the calling script.
senderruntime.MessageSender.
sendResponsefunction. Function to call (at most once) when you have a response. The argument should be any JSON-ifiable object. If you have more than oneonMessagelistener in the same document, then only one may send a response. This function becomes invalid when the event listener returns, unless you return true from the event listener to indicate you wish to send a response asynchronously (this will keep the message channel open to the other end untilsendResponseis called).
Returns:
boolean. Return true from the event listener if you wish to callsendResponseafter the event listener returns.
Browser compatibility
Examples
Example add-ons
Acknowledgements
This API is based on Chromium's chrome.runtime API. This documentation is derived from runtime.json in the Chromium code.
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