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Wednesday, 22 June 2016

JavaScript 有着很奇怪的命名史

1995 年,它作为网景浏览器(Netscape Navigator)的一部分首次发布,网景给这个新语言命名为 LiveScript。一年后,为了搭上当时媒体热炒 Java 的顺风车,临时改名为了 JavaScript (当然,Java 和 JavaScript 的关系,就和雷锋和雷锋塔一样 —— 并没有什么关系) 歪果仁的笑话怎么一点都不好...

译者注:wikipedia 的 JavaScript 词条 更详细的叙述了这段历史
1996 年,网景将 JavaScript 提交给 ECMA International(欧洲计算机制造商协会) 进行标准化,并最终确定出新的语言标准,它就是 ECMAScript。自此,ECMAScript 成为所有 JavaScript 实现的基础,不过,由于 JavaScript 名字的历史原因和市场原因(很显然 ECMAScript 这个名字并不令人喜欢……),现实中我们只用 ECMAScript 称呼标准,平时都还是使用 JavaScript 来称呼这个语言。
术语(译者注):
  • 标准(Standard): 用于定义与其他事物区别的一套规则
  • 实现(Implementation): 某个标准的具体实施/真实实践
不过,JavaScript 开发者们并不怎么在乎这些,因为在诞生之后的 15 年里,ECMAScript 并没有多少变化,而且现实中的很多实现都已经和标准大相径庭。其实在第一版的 ECMAScript 发布后,很快又跟进发布了两个版本,但是自从 1999 年 ECMAScript 3 发布后,十年内都没有任何改动被成功添加到官方规范里。取而代之的,是各大浏览器厂商们争先进行自己的语言拓展,web 开发者们别无选择只能去尝试并且支持这些 API。即使是在 2009 年 ECMAScript 5 发布之后,仍然用了数年这些新规范才得到了浏览器的广泛支持,可是大部分开发者还是写着 ECMAScript 3 风格的代码,并不觉得有必要去了解这些规范。
译者注:ECMAScript 第四版草案由于太过激进而被抛弃,Adobe 的 ActionScript 3.0 是 ECMAScript edition 4 的唯一实现( Flash 差点就统一 Web 了)
到了 2012 年,事情突然开始有了转变。大家开始推动停止对旧版本 IE 浏览器的支持,用 ECMAScript 5 (ES5) 风格来编写代码也变得更加可行。与此同时,一个新的 ECMAScript 规范也开始启动。到了这时,大家开始逐渐习惯以对 ECMAScript 规范的版本支持程度来形容各种 JavaScript 实现。在正式被指名为 ECMAScript 第 6 版 (ES6) 之前,这个新的标准原本被称为 ES.Harmony(和谐)。2015 年,负责制定 ECMAScript 规范草案的委员会 TC39 决定将定义新标准的制度改为一年一次,这意味着每个新特性一旦被批准就可以添加,而不像以往一样,规范只有在整个草案完成,所有特性都没问题后才能被定稿。因此,ECMAScript 第 6 版在六月份公布之前,又被重命名为了 ECMAScript 2015(ES2015)
目前,仍然有很多新的 JavaScript 特性或语法正在提议中,包括 decorators(装饰者)async-await(async-await 异步编程模型) 和 static class properties(静态类属性)。它们通常被称为 ES7,ES2016 或者 ES.Next 的特性,不过实际上它们只能被称作提案或者说可能性,毕竟 ES2016 的规范还没有完成,有可能全部都会引入,也有可能一个都没有。TC39 把一个提案分为 4 个阶段,你可以在 Babel 的官网 上查看各个提案目前都在哪个阶段了。
所以,我们该如何使用这一大堆术语呢?下面的列表或许能帮助到你:
  • ECMAScript:一个由 ECMA International 进行标准化,TC39 委员会进行监督的语言。通常用于指代标准本身。
  • JavaScript:ECMAScript 标准的各种实现的最常用称呼。这个术语并不局限于某个特定版本的 ECMAScript 规范,并且可能被用于任何不同程度的任意版本的 ECMAScript 的实现。
  • ECMAScript 5 (ES5):ECMAScript 的第五版修订,于 2009 年完成标准化。这个规范在所有现代浏览器中都相当完全的实现了。
  • ECMAScript 6 (ES6) / ECMAScript 2015 (ES2015):ECMAScript 的第六版修订,于 2015 年完成标准化。这个标准被部分实现于大部分现代浏览器。可以查阅这张兼容性表来查看不同浏览器和工具的实现情况。
  • ECMAScript 2016:预计的第七版 ECMAScript 修订,计划于明年夏季发布。这份规范具体将包含哪些特性还没有最终确定
  • ECMAScript Proposals:被考虑加入未来版本 ECMAScript 标准的特性与语法提案,他们需要经历五个阶段:Strawman(稻草人),Proposal(提议),Draft(草案),Candidate(候选)以及 Finished (完成)。
在这整个 Blog 中,我将把目前的 ECMAScript 版本称作 ES6(因为这是大部分开发者最习以为常的),把明年的规范称作 ES2016(因为,与 ES6/ES2015 不同,这个名字将在整个标准化过程中沿用)并且将那些还没有成为 ECMAScript 定稿或草案的未来语言概念称为 ECMAScript 提案或者 JavaScript 提案。我将尽我所能在任何可能引起困惑的场合沿用这篇文章.

一些资源

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JavaScript has a strange naming history. For its initial release in 1995 as part of Netscape Navigator, Netscape labeled their new language LiveScript, before renaming it to JavaScript a year later, hoping to capitalize on Java's popularity at the time (JavaScript has no actual relationship to Java). In 1996 Netscape submitted JavaScript to ECMA International for standardization. This eventually resulted in a new language standard, labeled ECMAScript. All major JavaScript implementations since have actually been implementations of the ECMAScript standard, but the term JavaScript has stuck for historical and marketing reasons 
. In the real world ECMAScript is usually used to refer to the standard while JavaScript is used when talking about the language in practice.

This has mostly been trivia for JavaScript developers, because ECMAScript didn't change much for the first 15 years of its existence, and real world implementations often differed significantly from the standard. After the initial version of ECMAScript, work on the language continued and two more versions were quickly published. But after ECMASCript 3 came out in 1999, there were no changes made to the official standard for a decade. Instead various browser vendors made their own custom extensions to the language, and web developers were left to try and support multiple APIs. Even after ECMAScript 5 was published in 2009, it took several years for wide browser support of the new spec, and most developers continued to write code in ECMAScript 3 style, without necessarily being aware of the standard.
Around 2012 things started to change. There was more of a push to stop supporting old Internet Explorer versions, and writing code in ECMAScript 5 (ES5) style became much more feasible. At the same time work was underway on a new ECMAScript standard, at which point it became much more common to start referring to JavaScript implementations in terms of their support for different ECMAScript standards. The new standard was originally named ES.Harmony, before eventually being referred to as ECMAScript 6th Edition (ES6). In 2015 TC39, the committee responsible for drafting the ECMAScript specifications, made the decision to move to a yearly model for defining new standards, where new features would be added as they were approved, rather than drafting complete planned out specs that would only be finalized when all features were ready. As a result ECMAScript 6th edition was renamed ECMAScript 2015 (ES2015) before it was published in June.
Currently there are several proposals for new features or syntax to be added to JavaScript. These include decoratorsasync-await, and static class properties. These are often refered to as ES7, ES2016, or ES.Next features, but should realistically be called proposals or possibilities, since the ECMAScript 2016 specification hasn't been written yet, and might include all or none of those features. TC39 divides proposals into 4 stages. You can see the current state of various proposals on Babel's website.
So where does that leave us in terms of terminology? The following list might be helpful:
  • ECMAScript: A language standardized by ECMA International and overseen by the TC39 committee. This term is usually used to refer to the standard itself.
  • JavaScript: The commonly used name for implementations of the ECMAScript standard. This term isn't tied to a particular version of the ECMAScript standard, and may be used to refer to implementations that implement all or part of any particular ECMASCript edition.
  • ECMAScript 5 (ES5): The 5th edition of ECMAScript, standardized in 2009. This standard has been implemented fairly completely in all modern browsers
  • ECMAScript 6 (ES6)/ ECMAScript 2015 (ES2015): The 6th edition of ECMAScript, standardized in 2015. This standard has been partially implemented in most modern browsers. To see the state of implementation by different browsers and tools, check outthese compatibility tables.
  • ECMAScript 2016: The expected 7th edition of ECMAScript. This is scheduled to be released next summer. The details of what the spec will contain have not been finalized yet
  • ECMAScript Proposals: Proposed features or syntax that are being considered for future versions of the ECMAScript standard. These move through a process of five stages: Strawman, Proposal, Draft, Candidate and Finished.
Going forward in this blog, I'll be referring to the recent ECMAScript version as ES6 (since that is how it is best known by most developers), next years spec as ES2016 (since that will be what it is called the whole way through its standardization process, unlike ES6/ES2015) and future language ideas that are not yet part of a draft or finalized spec as ECMAScript proposals or JavaScript proposals. I'll do my best to point back to this post in any cases that might be confusing.

More Resources

from http://benmccormick.org/2015/09/14/es5-es6-es2016-es-next-whats-going-on-with-javascript-versioning/