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.