At my current job I need to work a lot with Node.js backend services, and one thing is recurring - I need to simulate some delays in the code, mostly for testing purposes.
In the old days this was pretty problematic, we had the classic " callback hell ", which made the code very unreadable, sometimes had to refactor (copy-paste mostly) huge parts of the codebase, just to simulate some delay.
Nowadays the air is more fresh regarding asynchronous programming in the JavaScript economy, because we have Promises supported natively, and in newer versions of Node.js you get async-await, which we learned about in one of my previous posts (don't get fooled, the post is about the package `co`, which was essentially the equivalent of today's async-await).
So how do we simulate delays today? It's super easy actually, you just need to know that async-await is basically operating on top of Promises. Without any further discussion, here is the code:
await new Promise(resolve => setTimeout(resolve, 5000));
Let's look at what this codesnippet does.
await is going to wait (no pun intended) for a Promise, and until it resolves, it's not going to continue the execution flow.
So we create the Promise, where we just wait using the setTimeout method 5000 milliseconds (5s), and then resolve the Promise! Simple as that!
I think this is a pretty handy codesnippet, that I wish I knew before!
以上所述就是小编给大家介绍的《My current favourite trick in Node.js》,希望对大家有所帮助,如果大家有任何疑问请给我留言,小编会及时回复大家的。在此也非常感谢大家对 码农网 的支持!
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UML基础与Rose建模案例
吴建 / 人民邮电出版社 / 2004-10 / 29.00元
《UML 基础与Rose建模案例》介绍了用UML(统一建模语言)进行软件建模的基础知识以及Rational Rose工具的使用方法,其中,前8章是基础部分,对软件工程思想、UML的相关概念、Rational Rose工具以及RUP软件过程等进行了详细的介绍;后3章是案例部分,通过3个综合实例,对UML建模(以Rose为实现工具)的全过程进行了剖析;最后的附录中给出了UML中常用的术语、标准元素和元......一起来看看 《UML基础与Rose建模案例》 这本书的介绍吧!