ResizeObserverSize
The ResizeObserverSize interface of the Resize Observer API is used by the ResizeObserverEntry interface to access the box sizing properties of the element being observed.
Properties
The blockSize read-only property of the ResizeObserverSize interface returns the length of the observed element's border box in the block dimension. For boxes with a horizontal writing-mode, this is the vertical dimension, or height; if the writing-mode is vertical, this is the horizontal dimension, or width.
The inlineSize read-only property of the ResizeObserverSize interface returns the length of the observed element's border box in the inline dimension. For boxes with a horizontal writing-mode, this is the horizontal dimension, or width; if the writing-mode is vertical, this is the vertical dimension, or height.