javascript：如何从window.opener访问window.top？

Question

I am trying to refer to window.top in my popup window here http://www.globalrph.com/davescripts/popup.htm

once in the popup I want to access the main window's document but window.top is returning undefined.

Answer 1

To access your popup's opener use.

window.opener

To access your opener's top (eg your opener is in an iframe)

window.opener.top

Once at the opener window you want you can access the document to change its context, the location to manipulate the URL etc.

Answer 2

If you want to move your popup to the same top position as the opening browser window and centered horizontally to the size of the opening browser window, in modern browsers you can use:

window.moveTo(window.opener.screenX + (window.opener.outerWidth / 2) - (window.outerWidth / 2), window.opener.screenY)

outerWidth and screenX and screenY work in IE9 and above and in modern browsers.

moveTo has been around a long time.

In this case we're getting the left position of the opening browser window, calculating its center and subtracting half the width of the popup. That gives the center position. Then we use window.opener.screenY to get the top position of the opening browser window and setting the popup's top the same.

Many browsers have popup blockers turned on by default and will require the user to click a link to open a popup. I have this web application that opens a popup window to preview the results. A lot of web applications use a positioned div for dialogs. Not knowing your application, I really can't give advice as to the best approach to take.