I have access to a page template but no access to the header template (don’t ask me how!), I need to create an instant page redirect on that template. It’s needs to open in a new window.
It doesn’t really matter how it’s done just that it opens in a new window and please bear in mind I don’t have access to the header template.
I could be a bit off here (please correct me if i am) but,
you just the page to open a new page then something like this
See this for detailed usage of window.open.
You can pass html into the function as well.
<body onload="window.open(yourwindow)">
Or if you were just wanting a redirect to an existing page then
See this for detailed usage of window.location.
<body onload=window.location='www.yourlocation.com'>
Pass that whatever you want for parameters into the url.
Or if you were looking to grab some info from the page before you transition then you could just write a function that grabs the data you need from the header and pass that to the new page.