_ff-addon-snippet-copyOfRequestSource - This is a copy paste example of how to get a copy of the source code per request.

_ff-addon-snippet-copyOfRequestSource.js

/////// START - DO NOT EDIT
var {classes: Cc, interfaces: Ci, results: Cr, Constructor: CC, utils: Cu} = Components;
Cu.import('resource://gre/modules/Services.jsm');

var BinaryInputStream = CC('@mozilla.org/binaryinputstream;1', 'nsIBinaryInputStream', 'setInputStream');
var BinaryOutputStream = CC('@mozilla.org/binaryoutputstream;1', 'nsIBinaryOutputStream', 'setOutputStream');
var StorageStream = CC('@mozilla.org/storagestream;1', 'nsIStorageStream', 'init');

function TracingListener() {
	this.receivedChunks = []; // array for incoming data. holds chunks as they come, onStopRequest we join these junks to get the full source
	this.responseBody; // we'll set this to the 
	this.responseStatusCode;

	this.deferredDone = {
		promise: null,
		resolve: null,
		reject: null
	};
	this.deferredDone.promise = new Promise(function(resolve, reject) {
		this.resolve = resolve;
		this.reject = reject;
	}.bind(this.deferredDone));
	Object.freeze(this.deferredDone);
	this.promiseDone = this.deferredDone.promise;
}
TracingListener.prototype = {
	onDataAvailable: function(aRequest, aContext, aInputStream, aOffset, aCount) {
		var iStream = new BinaryInputStream(aInputStream) // binaryaInputStream
		var sStream = new StorageStream(8192, aCount); // storageStream // not sure why its 8192 but thats how eveyrone is doing it, we should ask why
		var oStream = new BinaryOutputStream(sStream.getOutputStream(0)); // binaryOutputStream

		// Copy received data as they come.
		var data = iStream.readBytes(aCount);
		this.receivedChunks.push(data);

		oStream.writeBytes(data, aCount);

		this.originalListener.onDataAvailable(aRequest, aContext, sStream.newInputStream(0), aOffset, aCount);
	},
	onStartRequest: function(aRequest, aContext) {
		this.originalListener.onStartRequest(aRequest, aContext);
	},
	onStopRequest: function(aRequest, aContext, aStatusCode) {
		this.responseBody = this.receivedChunks.join('');
		delete this.receivedChunks;
		this.responseStatus = aStatusCode;
		this.originalListener.onStopRequest(aRequest, aContext, aStatusCode);

		this.deferredDone.resolve();
	},
	QueryInterface: function(aIID) {
		if (aIID.equals(Ci.nsIStreamListener) || aIID.equals(Ci.nsISupports)) {
			return this;
		}
		throw Cr.NS_NOINTERFACE;
	}
};

var httpResponseObserver = {
	observe: function(aSubject, aTopic, aData) {
		var newListener = new TracingListener();
		aSubject.QueryInterface(Ci.nsITraceableChannel);
		newListener.originalListener = aSubject.setNewListener(newListener);
		/////// END - DO NOT EDIT
		newListener.promiseDone.then(
			function() {
				// no error happened
				console.log('yay response done:', newListener.responseBody);
			},
			function(aReason) {
				// promise was rejected, right now i didnt set up rejection, but i should listen to on abort or bade status code then reject maybe
			}
		).catch(
			function(aCatch) {
				console.error('something went wrong, a typo by dev probably:', aCatch);
			}
		);
	}
};

Services.obs.addObserver(httpResponseObserver, 'http-on-examine-response', false);
// Services.obs.removeObserver(httpResponseObserver, 'http-on-examine-response'); // call this when you dont want to listen anymore

README

Rev1

• Works, copy paste to scratchpad, like this: https://www.youtube.com/watch?v=oo4STWceGTM
• As a person copy pasting this, you should not have to edit anything in the TraceableListener, you should only add code in place of console.log('yay response done:', newListener.responseBody);
  • You should also pick where you want to run the Services.obs.addObserver(httpResponseObserver, 'http-on-examine-response', false); and the removal of it
• Because this gist uses the new promise method, it works only as of Firefox 30
• Based on:
  • GitHubGIST :: kewisch / TracedRequest.js
  • Stackoverflow :: nsITraceableChannel, Intercept HTTP Traffic code

Rev2

• Formatting

Rev3

• Formatting, had mixed tabs and spaces for indentation

Rev4

• Pointed out the "do not edit" section for those that are just copy/pasting this.

Rev5

• More formatting, blocked all the do not edit stuff at top

Rev6

• According to the interface spec nsIStorageStream.init doesn't have a third argument: https://dxr.mozilla.org/mozilla-central/source/xpcom/io/nsIStorageStream.idl#31 - Thanks @freaktechnik

• Thanks @tew for the catch

  compare

  ["some wor","ds that", " are in data"].join(); // "some wor,ds that, are in data"
  

  with

  ["some wor","ds that", " are in data"].join(''); // "some words that are in data"