proxy.onRequest
Fired when a web request is about to be made, to give the extension an opportunity to proxy it.
This event is closely modeled on the events defined in the webRequest
API. Like those events, its addListener()
function takes three arguments:
- the listener that is called when the event is fired.
- a
RequestFilter
object controlling which requests cause the event to fire. - an array of strings to control other aspects of the event's behavior.
The event is fired before any of the webRequest
events for the same request.
When the event is fired, the listener is called with an object containing information about the request. The listener returns a proxy.ProxyInfo
object representing a proxy to use (or an array of proxy.ProxyInfo
objects, enabling the browser to fail over if a proxy is unreachable).
To use proxy.onRequest
, an extension must have the "proxy" API permission and the host permission for the URLs of the requests that it intercepts, which means that the match patterns in the filter
argument must be a subset of the extension's host permissions.
Syntax
browser.proxy.onRequest.addListener(
listener, // function
filter, // object
extraInfoSpec // optional array of strings
)
browser.proxy.onRequest.removeListener(listener)
browser.proxy.onRequest.hasListener(listener)
Events have three functions:
addListener(listener, filter, extraInfoSpec)
-
Adds a listener to this event.
removeListener(listener)
-
Stop listening to this event. The
listener
argument is the listener to remove. hasListener(listener)
-
Check whether
listener
is registered for this event. Returnstrue
if it is listening,false
otherwise.
addListener syntax
Parameters
listener
-
The function that is called when this event occurs. The function is passed a single argument, which is a
proxy.RequestDetails
object containing details of the request.The listener can return any of:
- a
proxy.ProxyInfo
object. - an array of
proxy.ProxyInfo
objects. - a
Promise
that resolves to aProxyInfo
object. - a
Promise
that resolves to an array ofProxyInfo
objects.
If the listener returns an array, or a Promise that resolves to an array, then all
ProxyInfo
objects after the first one represent failovers: if the proxy at position N in the array is not reachable when itsProxyInfo.failoverTimeout
expires the browser will try the proxy at position N+1.If there is an error specifying the
proxy.ProxyInfo
objects, thenproxy.onError
is called. - a
filter
-
webRequest.RequestFilter
. A set of filters that restricts the events that are sent to the listener. extraInfoSpec
Optional-
array
ofstring
. Extra options for the event. Pass"requestHeaders"
to include the request headers in thedetails
object passed to the listener.
Browser compatibility
BCD tables only load in the browser
Examples
This code intercepts requests to <all_urls>
, and proxies them if they are not for a top-level frame.
function shouldProxyRequest(requestInfo) {
return requestInfo.parentFrameId !== -1;
}
function handleProxyRequest(requestInfo) {
if (shouldProxyRequest(requestInfo)) {
console.log(`Proxying: ${requestInfo.url}`);
return { type: "http", host: "127.0.0.1", port: 65535 };
}
return { type: "direct" };
}
browser.proxy.onRequest.addListener(handleProxyRequest, {
urls: ["<all_urls>"],
});