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，句子必須用倒裝結(jié)構(gòu)：
　hardly / scarcely had i got home when it began to rain.
　no sooner had i got home than it began to rain.