无论屏幕分辨率如何，我如何居中javascript css弹窗div ?

I have the following code that opens a new popup window while disabling the background, the problem is that I have to position this so that it's 100px from the top (already got that through the CSS #dialog) and also in the center of the screen, no matter what the user's resolution is?I have the following code that opens a new popu