Pop-Up Window, Center Screen

Question

I'm using the following code to open a pop-up window in a Google Chrome extension, my one question is, how do I get the pop-up window to open in the centre of the users screen?

 <script>
  chrome.browserAction.onClicked.addListener(function() {
    var left = (screen.width/2)-(w/2);
    var top = (screen.height/2)-(h/2); 
  chrome.windows.create({'url': 'redirect.html', 'type': 'popup', 'width': 440, 'height': 220, 'left': '+left+', 'top': '+top+', } , function(window) {
   });
});
  </script>

I've also tried this, which resulted in no such luck.

  <script>
  chrome.browserAction.onClicked.addListener(function() {
  chrome.windows.create({'url': 'redirect.html', 'type': 'popup', 'width': 440, 'height': 220, 'left': (screen.width/2)-(w/2), 'top': (screen.height/2)-(h/2), } , function(window) {
   });
});
  </script>

Answer 1

When you see var obj = {property: value} structure in JS it is an object creation. In your code you are trying to pass an object containing window properties to chrome.windows.create() function.

Correct code should be:

chrome.browserAction.onClicked.addListener(function() {
    var w = 440;
    var h = 220;
    var left = (screen.width/2)-(w/2);
    var top = (screen.height/2)-(h/2); 

    chrome.windows.create({'url': 'redirect.html', 'type': 'popup', 'width': w, 'height': h, 'left': left, 'top': top} , function(window) {
    });
});