ResizeObserver.observe()

The observe() method of the ResizeObserver interface starts observing the specified Element or SVGElement.

Inputs: target A reference to an Element or SVGElement to be observed. options An options object allowing you to set options for the observation. Currently this only has one possible option that can be set: box Sets which box model the observer will observe changes to. Possible values are: content-box (the default) Size of the content area as defined in CSS. border-box Size of the box border area as defined in CSS. device-pixel-content-box The size of the content area as defined in CSS, in device pixels, before applying any CSS transforms on the element or its ancestors.