Returns an up.Layer object for the given element or layer option.
Looking up the layer of an element
Passing an element will return the layer containing that element:
let element = document.querySelector(...)
up.layer.get(element) // returns the element's layer
If the given element is detached, or part of a closing overlay, undefined is returned.
Getting the nth layer
Pass a number to return the up.Layer object at that index:
up.layer.get(0) // returns the root layer
up.layer.get(1) // returns the first overlay
Resolving a layer option
Pass any layer option to return the up.Layer object
of the first layer matching that option:
up.layer.get('front') // returns the front layer
To look up one of multiple layer options, separate the values using or:
// returns the parent layer, or the root if we're already on root:
up.layer.get('parent or root')
Existing up.Layer objects are returned
Passing an existing up.Layer object will return it unchanged:
let layer = up.layer.root
up.layer.get(layer) // returns the given layer
Missing values return the current layer
Passing null or undefined will return the current layer:
up.layer.get(undefined) // returns the current layer
