JavaScript window.open only if the window does not already exist

Question

I have an application that opens a new window on clicking a link. This spawns a page that holds a Java applet. The problem I am having is that clicking the same link reloads the page, which resets the Java application. Is there any way to trap this? Two solutions that would be acceptable are:

1. Allow multiple windows to be opened from the click handler
2. Ignore subsequent requests if the window is already open

Apologies for being a Javascript newbie - it's not really my main thing.

The code attached to the handler is

function launchApplication(l_url, l_windowName) {   var l_width = screen.availWidth;   var l_height = screen.availHeight;    var l_params = 'status=1' +                  ',resizable=1' +                  ',scrollbars=1' +                  ',width=' + l_width +                  ',height=' + l_height +                  ',left=0' +                  ',top=0';    winRef = window.open(l_url, l_windowName, l_params);   winRef.moveTo(0,0);   winRef.resizeTo(l_width, l_height); } 

EDIT:

Thanks for the replies - I modified the suggestions slightly so that I could have more than one URL opened via the function.

EDIT2: There is another version of this code at Check for a URL open on another window

var g_urlarray = [];  Array.prototype.has = function(value) {     var i;     for (var i in this) {         if (i === value) {             return true;         }     }     return false; };   function launchApplication(l_url, l_windowName) {   var l_width = screen.availWidth;   var l_height = screen.availHeight;   var winRef;    var l_params = 'status=1' +                  ',resizable=1' +                  ',scrollbars=1' +                  ',width=' + l_width +                  ',height=' + l_height +                  ',left=0' +          ',top=0';   if (g_urlarray.has(l_url)) {     winRef = g_urlarray[l_url];   }   alert(winRef);   if (winRef == null || winRef.closed) {       winRef = window.open(l_url, l_windowName, l_params);       winRef.moveTo(0,0);       winRef.resizeTo(l_width, l_height);       g_urlarray[l_url] = winRef;   } } 

Answer 1

I'd do it like this - basically store all the referenced opened windows on the function itself. When the function fires, check if the window doesn't exist or has been close - of so, launch the popup. Otherwise, focus on the existing popup window for that request.

function launchApplication(l_url, l_windowName) {   if ( typeof launchApplication.winRefs == 'undefined' )   {     launchApplication.winRefs = {};   }   if ( typeof launchApplication.winRefs[l_windowName] == 'undefined' || launchApplication.winRefs[l_windowName].closed )   {     var l_width = screen.availWidth;     var l_height = screen.availHeight;      var l_params = 'status=1' +                    ',resizable=1' +                    ',scrollbars=1' +                    ',width=' + l_width +                    ',height=' + l_height +                    ',left=0' +                    ',top=0';      launchApplication.winRefs[l_windowName] = window.open(l_url, l_windowName, l_params);     launchApplication.winRefs[l_windowName].moveTo(0,0);     launchApplication.winRefs[l_windowName].resizeTo(l_width, l_height);   } else {     launchApplication.winRefs[l_windowName].focus()   } } 

Answer 2

You need to perform 2 tests... 1 check if the popup window is defined, and 2 check if it was closed.

if(typeof(winRef) == 'undefined' || winRef.closed){   //create new   winRef = window.open(....); } else {   //it exists, load new content (if necs.)   winRef.location.href = 'your new url';   //give it focus (in case it got burried)   winRef.focus(); }