What to do if the child element needs to be positioned relative to the parent element and cannot be stretched by the element

Today, after the child element is positioned relative to the parent element, the parent element cannot be opened, because after the absolute positioning, the child element has moved away from the document flow so that the parent element can not be opened with its own height, this time only with JS to solve the problem;

function Psize () {
$ ("parent element"). CSS (' height ', $ ("child element"). Innerheight ());
}

Above is a function that is encapsulated and can be used by a call.

Height and innerheight The specific situation, please see an essay.

What to do if the child element needs to be positioned relative to the parent element and cannot be stretched by the element