javascript – 节点版本8中Async / Await的性能指南
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async / await可用于节点版本8.代码在nodejs中首次是线性的,本机.那很好.之前很多文章都声称,在v8 javascript引擎中,没有优化try / catch块的功能.现在,async / await需要try / catch块来处理错误.那么,作为开发人员需要做些什么才能保持相同的性能？
解决方法:
try / catch在V8 5.3(Node v7.x及更高版本)的commit 9aac80f中收到了TurboFan优化.这意味着try / catch性能不佳的历史性陈述不再适用.
从V8 blog post开始：
In the past V8’s had difficulties optimizing the kind of language features that are found in ES2015+. For example, it never became feasible to add exception handling (i.e.
try/catch/finally) support to Crankshaft, V8’s classic optimizing compiler. This meant V8’s ability to optimize an ES6 feature likefor...of, which essentially has an implicit finally clause, was limited. Crankshaft’s limitations and the overall complexity of adding new language features to full-codegen, V8’s baseline compiler, made it inherently difficult to ensure new ES features were added and optimized in V8 as quickly as they were standardized.Fortunately, Ignition and TurboFan (V8’s new interpreter and compiler pipeline), were designed to support the entire JavaScript language from the beginning, including advanced control flow, exception handling, and most recently
for...ofand destructuring from ES2015. The tight integration of the architecture of Ignition and TurboFan make it possible to quickly add new features and to optimize them fast and incrementally.
异步函数中的try / catch只是对Promise .then和.catch方法的合成糖,因此性能由底层的Promise实现决定. Bluebird claims具有比原生Promise实现更好的性能,因此理论上 – 如果Bluebird声称的是真的 – 通过使用Bluebird的Promise实现覆盖原生Promise实现,您将获得更好的尝试/捕获性能.
例如,在Node：const Promise = require(“bluebird”)或global.Promise = require(“bluebird”)中全局覆盖它.
但请注意,这可能会在未来发生变化,因为最初的Promise实现是在JavaScript中,但最近已在C中重新实现,因为可以在错误#5343中进行跟踪.
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