I studied the height adaptive problem of div css_Experience exchange

Div css is still quite difficult to do. It’s troublesome to realize the adaptive height of the upper and lower divs. After checking the information, I found that it is possible to adjust the upper and lower heights as percentages. I want to realize that the above div has a specific pixel height. Below is the adaptive remaining percentage. I have done it myself and still need to use js. I don’t know if it is stupid. If you have a good method, please post it.