This feature is experimental. It may be changed or removed in a future version.
Your target selectors may use this pseudo-selector to replace the layer's topmost swappable element.
The topmost swappable element is the first child of the layer's container element.
For the root layer it is the <body>
element. For an overlay
it is the target with which the overlay was opened with.
In canonical usage the topmost swappable element is often a main element.
The following will replace the <body>
element in the root layer,
and the topmost swappable element in an overlay:
up.render(':layer', { url: '/page2' })