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How can I check whether an application is installed from a web browser?

This is for Windows.
I have a flash application I am converting to AIR. I built a captive installer using NSIS and it works fine. However I would like to have an icon on a website which checks if the application is already installed and ask the user if they wish to run it. If it is not installed, they get the option to download it.
I am fairly certain this is doable, because Zoom and GoToMeeting both do this.
My searching skills seem to be failing me when looking for this.
Edit:
It appears the best/only way to do this is to create a custom protocol for the application. Something like DoDaApp://.
Which brings up the next set of questions;
How to create an NSIS file which will create the appropriate registry entries on the client computer? As a user, not admin.
How to check if the protocol is currently installed on the computer?

This is a partial answer as it does not work in Edge. I'll explain the issue below.
As recommended in How to detect browser's protocol handlers you can use timeout & blur event handlers. Here is my interpretation of the code;
function checkCustomProtocol(inProtocol,inInstalLink,inTimeOut)
{
var timeout = inTimeOut;
window.addEventListener('blur',function(e)
{
window.clearTimeout(timeout);
}
)
timeout = window.setTimeout(function()
{
console.log('timeout');
window.location = inInstalLink;
}, inTimeOut
);
window.location = inProtocol;
}
Microsoft Edge is ever so helpful by popping up a dialog box telling you "You'll Need a new app to open this" which "blurs" the screen, not allowing download of the file.
So I will be posting another question on how to make it work in Edge. I have reviewed ismailhabib's code but the known issues section says it doesn't work with Edge either.

Here is a more complete answer. It has been lightly tested in IE 11, Microsoft Edge, Chrome and Firefox. I also added comments;
/*
checkCustomProtocol - check if custom protocol exists
inProtocol - URL of application to run eg: MyApp://
inInstallLink - URL to run when the protocol does not exist.
inTimeOut - time in miliseconds to wait for application to Launch.
*/
function checkCustomProtocol(inProtocol,inInstalLink,inTimeOut)
{
// Check if Microsoft Edge
if (navigator.msLaunchUri)
{
navigator.msLaunchUri(inProtocol, function ()
{
//It launched, nothing to do
},
function()
{
window.location = inInstalLink; //Launch alternative, typically app download.
}
);
}
else
{
// Not Edge
var timeout = inTimeOut;
//Set up a listener to see if it navigates away from the page.
// If so we assume the papplication launched
window.addEventListener('blur',function(e)
{
window.clearTimeout(timeout);
}
)
//Set a timeout so that if the application does not launch within the timeout we
// assume the protocol does not exist
timeout = window.setTimeout(function()
{
console.log('timeout');
window.location = inInstalLink; //Try to launch application
}, inTimeOut
);
window.location = inProtocol; //Launch alternative, typically app download.
}
}

Capture screen -- chrome.desktopCapture.chooseDesktopMedia fails -- PNacl extension

I'm trying to use the desktopCapture API in the following manner.
chrome.desktopCapture.chooseDesktopMedia(
["screen", "window"], onAccessApproved);
chrome.desktopCapture shows as undefined when I set a breakpoint and inspect it. Permissions in my manifest file are as follows:-
"permissions": ["desktopCapture", "notifications" ]
Common causes for failure of this API are listed here as
a permission is missing in the application's manifest.json file
the API is defined on a newer version of Chrome then the current runtime
docs inherited from ChromeApi
And I don't have those problems.
My Chrome version is 43.0.2357.124 m
Pepper version is 43
FYI, I am trying to develop a Chrome extension to capture the screen using PNacl, and have borrowed from the media_stream_video example downloaded from here. But I haven't even gotten to sending a message to the pexe side yet. I'm still stuck at chrome.desktopCapture.chooseDesktopMedia returning undefined.

You need to call chrome.desktopCapture.chooseDesktopMedia from the background script running in the context of the extension. This Sample shows a simple method to use the extension to get screen media.
Keep in mind that this is callback based, so you get access to the stream id from the callback.
This runs in the context of your page (see full example here):
// check that the extension is installed
if (sessionStorage.getScreenMediaJSExtensionId) {
// send a message to your extension requesting media
chrome.runtime.sendMessage(sessionStorage.getScreenMediaJSExtensionId,
{type:'getScreen', id: 1}, null,
function (data) {
if (data.sourceId === '') { // user canceled
// handle error
} else {
constraints.video.mandatory.chromeMediaSourceId = data.sourceId;
getUserMedia(constraints, callback);
}
}
);
}
And this run in the context of your extension (see full example here):
chrome.runtime.onMessageExternal.addListener(function (message, sender, callback) {
switch(message.type) {
case 'getScreen':
var pending = chrome.desktopCapture.chooseDesktopMedia(message.options || ['screen', 'window'],
sender.tab, function (streamid) {
// communicate this string to the app so it can call getUserMedia with it
message.type = 'gotScreen';
message.sourceId = streamid;
callback(message);
return false;
});
return true; // retain callback for chooseDesktopMedia result
}
});

how to detect the mobile connection is 2G/3G/WIFI using javascript

i have a similar requirement as in link below but i have to handle it by using JavaScript. where i have to detect whether the mobile internet connection is 2g/3g or it is WIFI . based on connection i have to perform diffent operations..
note : mobile can b of any OS like andriod/ iOS/BB .. i need to handle any mobile OS.
Is there a way to detect what kind of connection I'm using ? WiFi, 3G or Ethernet?
request masters to help me with inputs. thanks :)

Network Information API (This is an experimental technology):
The Network Information API provides information about the system's
connection, which is in term of general connection type (e.g., 'wifi',
'cellular', etc.). This can be used to select high definition content
or low definition content based on the user's connection. The entire
API consists of the addition of the domxref("NetworkInformation")
interface and a single property to the Navigator interface:
Navigator.connection.
var connection = navigator.connection || navigator.mozConnection || navigator.webkitConnection;
var type = connection.type;
function updateConnectionStatus() {
alert("Connection type is change from " + type + " to " + connection.type);
}
connection.addEventListener('typechange', updateConnectionStatus);

I wrote a small utility to do this. You can try it here
http://ashanbh.github.io/detectClientSpeed/example2.html
and fork it on github: https://github.com/ashanbh/detectClientSpeed
Usage:
<script src="scripts/require.js"></script>
<script>
requirejs(['scripts/detectSpeed'], function (detectSpeed) {
//Callback to receive timing information
var callback = function (timings) {
console.log(timings);
}
detectSpeed.startSpeedCheck("https://s3-us-west-1.amazonaws.com/amit.shanbhag/3g/coffee-apple-iphone-laptop.jpg", callback);
});
</script>

Identify tab that made request in Firefox Addon SDK

I'm using the Firefox Addon SDK to build something that monitors and displays the HTTP traffic in the browser. Similar to HTTPFox or Live HTTP Headers. I am interested in identifying which tab in the browser (if any) generated the request
Using the observer-service I am monitoring for "http-on-examine-response" events. I have code like the following to identify the nsIDomWindow that generated the request:
const observer = require("observer-service"),
{Ci} = require("chrome");
function getTabFromChannel(channel) {
try {
var noteCB= channel.notificationCallbacks ? channel.notificationCallbacks : channel.loadGroup.notificationCallbacks;
if (!noteCB) { return null; }
var domWin = noteCB.getInterface(Ci.nsIDOMWindow);
return domWin.top;
} catch (e) {
dump(e + "\n");
return null;
}
}
function logHTTPTraffic(sub, data) {
sub.QueryInterface(Ci.nsIHttpChannel);
var ab = getTabFromChannel(sub);
console.log(tab);
}
observer.add("http-on-examine-response", logHTTPTraffic);
Mostly cribbed from the documentation for how to identify the browser that generated the request. Some is also taken from the Google PageSpeed Firefox addon.
Is there a recommended or preferred way to go from the nsIDOMWindow object domWin to a tab element in the SDK tabs module?
I've considered something hacky like scanning the tabs list for one with a URL that matches the URL for domWin, but then I have to worry about multiple tabs having the same URL.

You have to keep using the internal packages. From what I can tell, getTabForWindow() function in api-utils/lib/tabs/tab.js package does exactly what you want. Untested code:
var tabsLib = require("sdk/tabs/tab.js");
return tabsLib.getTabForWindow(domWin.top);

The API has changed since this was originally asked/answered...
It should now (as of 1.15) be:
return require("sdk/tabs/utils").getTabForWindow(domWin.top);

As of Addon SDK version 1.13 change:
var tabsLib = require("tabs/tab.js");
to
var tabsLib = require("sdk/tabs/helpers.js");

If anyone still cares about this:
Although the Addon SDK is being deprecated in support of the newer WebExtensions API, I want to point out that
var a_tab = require("sdk/tabs/utils").getTabForContentWindow(window)
returns a different 'tab' object than the one you would typically get by using
worker.tab in a PageMod.
For example, a_tab will not have the 'id' attribute, but would have linkedPanel property that's similar to the 'id' attribute.

Can javascript access a filesystem? [duplicate]

This question already has answers here:
Local file access with JavaScript
(14 answers)
Closed 8 years ago.
I was pretty sure the answer was NO, and hence google gears, adobe AIR, etc.
If I was right, then how does http://tiddlywiki.com work? It is persistent and written in javascript. It is also just a single HTML file that has no external (serverside) dependencies. WTF? Where/how does it store its state?

Tiddlywiki has several methods of saving data, depending on which browser is used. As you could see in the source.
If ActiveX is enabled, it uses Scripting.FileSystemObject.
On Gecko-based browsers, it tries to use UniversalXPConnect.
If Java is enabled, it uses the TiddlySaver Java applet.
If Java LiveConnect is enabled, it tries to use Java's file classes.

HTML5's File[1], FileWriter[2], and FileSystem[3] APIs are available in the latest Developer channel of Google Chrome. The FileSystem API lets you read/write to a sandbox filesystem within a space the browser knows about. You cannot, for example, open 'My Pictures' folder on the user's local FS and read/write to that. That's something in the works, but it won't be ready for a while. Example of writing a file:
window.requestFileSystem(
TEMPORARY, // persistent vs. temporary storage
1024 * 1024, // 1MB. Size (bytes) of needed space
initFs, // success callback
opt_errorHandler // opt. error callback, denial of access
);
function initFs(fs) {
fs.root.getFile('logFile.txt', {create: true}, function(fileEntry) {
fileEntry.createWriter(function(writer) { // FileWriter
writer.onwrite = function(e) {
console.log('Write completed.');
};
writer.onerror = function(e) {
console.log('Write failed: ' + e.toString());
};
var bb = new BlobBuilder();
bb.append('Lorem ipsum');
writer.write(bb.getBlob('text/plain'));
}, errorHandler);
}
}
Check out this HTML5 Storage slide deck for more code snippets.

It uses a java file references like this:
drivers.tiddlySaver = {
name: "tiddlySaver",
deferredInit: function() {
if(!document.applets["TiddlySaver"] && !$.browser.mozilla && !$.browser.msie && document.location.toString().substr(0,5) == "file:") {
$(document.body).append("<applet style='position:absolute;left:-1px' name='TiddlySaver' code='TiddlySaver.class' archive='TiddlySaver.jar' width='1'height='1'></applet>");
}
},
isAvailable: function() {
return !!document.applets["TiddlySaver"];
},
loadFile: function(filePath) {
var r;
try {
if(document.applets["TiddlySaver"]) {
r = document.applets["TiddlySaver"].loadFile(javaUrlToFilename(filePath),"UTF-8");
return (r === undefined || r === null) ? null : String(r);
}
} catch(ex) {
}
return null;
},
saveFile: function(filePath,content) {
try {
if(document.applets["TiddlySaver"])
return document.applets["TiddlySaver"].saveFile(javaUrlToFilename(filePath),"UTF-8",content);
} catch(ex) {
}
return null;
}
}

Technically you can do
netscape.security.PrivilegeManager.enablePrivilege('UniversalBrowserWrite');
in a netscape-compatible browser (Firefox, Mozilla, Netscape), and it will ask the user* whether or not to allow filesystem access, but this is not portable.
*once per browser process

Can javascript access a filesystem?
Not outside of the sandbox area mentioned above, to the best of my knowledge. However, it can access a signed java applet that has callable public methods which can get to all files. I have done it and it works fine and is cross browser.
The signing part is somewhat involved and for professional use you might need to pay for a code signing certificate which authorises your identity. Get it from some place like Verisign. That way users at least know who the applet is written by (if that helps). You can sign it yourself for free but one of those "possible security risk" popups will occur at first use for authorisation by the user.
You would think that such signed applets for file writing would exist already for download but I couldn't find any via searching. If they did, you could just plug it in your page, learn the API and off you go.

The answer is indeed NO. Java applets, and the dreaded ActiveX plugins are usually used if this is required