The window object is one level higher than the document object in the JavaScript object hierarchy.
The window object can manipulate the current window as well as create new window instances.
If window B is created by window A, window B is considered a child of window A.
<html>
<body>
<script language="JavaScript">
<!--
function create(){
open("http://www.java2s.com", "myChild");
}
-->
</script>
<form name="form1">
<input type="button" value="Create Child" onClick='create()'>
</form>
</body>
</html>
The name of the child window is "myChild".
Any values in the child window are referenced using the name of the parent window.
The parent has total control of its immediate child window and any subsequent child (grandchild) windows.
If the parent window is destroyed, all control for the remaining child windows is lost.
A child window can find out who its parent is by using the opener method.
You use the opener method as shown in the following:
var name = window.opener.document.name;
This will return the name of the parent document to the name variable.
You can use multiple instances of opener if you have several levels of windows.
If a grandchild wanted to reference its grandparent, it could do so by simply adding another level.
window.opener.opener.document.form1.textbox.value
For a window to refer to its own properties, you can use the window self property.
Suppose you wanted to set a textbox value within a form document in a window.
self.document.formName.textbox.value = "JavaScript is cool";