Custom Buttons (FF) - open URL from current tab in any browser

CB.openInBrowser.code.js

// IE
this.openCurrentUrl("c:\\Program Files\\Internet Explorer\\iexplore.exe");
// Firefox Developer Edition
this.openCurrentUrl("C:\\Program Files\\Mozilla\\Firefox Developer Edition\\firefox.exe");
// Chrome
this.openCurrentUrl("C:\\Program Files (x86)\\Google\\Chrome\\Application\\chrome.exe");
// Edge
// for whatever reason this doesn't work for local files (i.e. "file:///...")
this.openCurrentUrl("c:\\windows\\system32\\cmd.exe", ["/c", "start", "microsoft-edge:%u"]);

CB.openInBrowser.init.js

/*Init*/

/**
@param application Browser executable path. Note that this needs to be a full path.
@param args If empty then defaults to `["%u"]` - which means the browser executable takes one parameter and its the URL.
*/
this.openCurrentUrl = function (application, args) {
	// init
	var localFile = Components.classes["@mozilla.org/file/local;1"].createInstance(Components.interfaces.nsILocalFile);
	var process = Components.classes["@mozilla.org/process/util;1"].createInstance(Components.interfaces.nsIProcess);

	// get url
	var currentUrl = gBrowser.currentURI.spec;

	// default arg format
	if (typeof args !== "object") {
		args = ["%u"];
	}
	
	// replace "%u" in args
	for (var i = 0; i < args.length; i++) {
		args[i] = args[i].replace('%u', currentUrl);
	}

	// run
	localFile.initWithPath(application);
	process.init(localFile);
	process.run(false, args, args.length);
}