to be a good thing to do, or to be a lucky thing to happen or be done

It's just as well you're not here - you wouldn't like the noise. 幸好你没在这儿——你不会喜欢那种噪声的。

He left at three, which was just as well or he'd have missed the plane. 他3点钟出发的，时间刚刚好，否则就赶不上飞机了。

It would be as well to check the small print. 最好再看一下用小号字印的细则。