大学英语四级语法大全目录
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.
From:https://www.zgghmh.com/CET-4/20001161.asp