当否定词语放句首时,句子用倒装.“Hardly +had +主语＋done…when / before + 主语＋did.”
// “主语＋had +hardly + done…when / before +主语＋did.”
例如：
①Hardly had she had supper when she went out. “她一吃完晚饭就出去了.”
②She had hardly had supper when she went out. （同上） 两个用法一样,可以互换,都表示“刚一……就……”.
如果要讲细微区别的话,就是hardly ..when ..更紧凑一些,意思是“几乎未来得及做完A这件事,紧接着就开始做B这件事”.
而no sooner.. than意思是“刚做完A这件事,就做B这件事”.