javascript - Getting CSS Calc percentages to update during resize -

i have series of panels have css calc/percentage based heights , widths. panels accurately , smoothly resize after window size has changed.

    height: calc(50% - 5px); 

however, wondering if there way have panels resize while window being resized instead of after. don't want use kind of js calculation this! if there dom api setting or way of manually re-firing calc() function on resize, acceptable.

edit: don't want calculating widths , heights in js. else fine.

does know way of doing this?