Document: caretRangeFromPoint() method

The 
caretRangeFromPoint() method of the Document interface returns a Range object for the document fragment under the specified coordinates.
This method predates the concept of shadow DOM, and will return unpredictable and implementation-specific results in a document that contains ShadowRoot objects.
Use caretPositionFromPoint() instead on supporting browsers because it is a standard method that can return the caret position from within ShadowRoot instances, provided the relevant shadow roots are passed in its 
options parameter.
Syntax
caretRangeFromPoint(x, y)
Parameters
x
: A horizontal position within the current viewport.
y
: A vertical position within the current viewport.
Return value
One of the following:
A Range.
null, if x or y are negative, outside the viewport, or there is no text entry node.
Examples
Visit the Document.caretPositionFromPoint() page to view a live sample of this method.
Specifications
Not part of any specification.
Browser compatibility
See also
Document.caretPositionFromPoint()