as it is 原本是个方式状语，现在成为一个英语习语，其过去时是as it was，其完成时是as it has (had) been。基本意思是“按照现在的样子；像目前的现状；根据现在情况看，照目前的情况看来”。

as it was和as it had been，在时间上指过去，意为“按照当时的样子；像那时的现状；根据当时情况看，照那个时候的情况看来”。

稍加分析我们就看出，它实际是as引导的方式状语从句，as的意思“按照......样子，像......那样”。

Leave it as it is.  照现在的样子把它放在那儿。

Don't shut the door; it's all right as it is.  不要关门，原样开着好。

Except for the loss of his miraculous powers, everything was back as it had been.  除了失去他那不可思议的能力之外，一切都回到了以往的状况。

I looked around the hotel parlour, and now it was restored as it was in 1927.   我看了看饭店的客厅，现在已恢复到1927年的样子。

Yes, the economy is growing instead of shrinking, as it was in 2008 and the beginning of 2009.  是的，我们的经济已经开始增长，而不是像2008年至2009年初所经历的萎缩。

As the years passed, most Americans were able to return to life as it had been before Nine-Eleven. 随着时间的推移，大部分的美国人民能够从悲痛中解脱出来，并重归“9.11”之前正常的生活。

I tried and failed to remember her face as it had been during the trial.  我怎么也想不起她在审判期间的那幅面孔了。

【补充解答】

Britain is not enjoying such prosperity as it was in the mid-1980s.

补充一下，刚才解答时没有看见前面有such。既然如此，as it was in the mid-1980s 就是一个定语从句。as 指代prosperity，而且做了从句的宾语。

Britain is not enjoying such prosperity as it was in the mid-1980s. 等于：

Britain is not enjoying such prosperity as it was enjoying in the mid-1980s.

当先行词前有as, so, such, the same 等修饰时，关系代词常用as，它在从句中作主语或宾语。

    The explorer took only such men and things as he really needed into the jungle.

    这个探险者进入丛林时仅带了一些他确实需要的人和东西。（as作needed的宾语）

    Such people as have made great contributions to the world should be greatly respected.

    那些对世界做出巨大贡献的人应受到极大的尊重。（as作主语）

    You may take as many chairs as you need.

    你需要多少椅子就拿走多少椅子。（as作need的宾语）

    My parents have not so much money as I want.

    我父母没有我需要的那么多钱。（as作want的宾语）

    This is the same cellphone as I lost yesterday. （as作lost的宾语）

    这与我昨天丢的那部手机一样。