hardly/scarcely…when/before, no sooner…than 和as soon as都可以表示"一…就…"的意思，例：
I had hardly / scarcely got home when it began to rain. I had no sooner got home than it began to rain. As soon as I got home, it began to rain.
注意：如果hardly, scarcely 或no sooner置于句首，句子必须用倒装结构： Hardly / Scarcely had I got home when it began to rain. No sooner had I got home than it began to rain.