TypeScript 3.0: unknown 类型 #5929

shixi-li · 2019-06-09T07:38:17Z

译文翻译完成，resolve #5863

smilemuffie · 2019-06-10T06:14:38Z

校对认领

fanyijihua · 2019-06-10T06:14:41Z

@smilemuffie 好的呢 🍺

Usey95 · 2019-06-10T10:02:54Z

校对认领

fanyijihua · 2019-06-10T10:02:55Z

@Usey95 妥妥哒 🍻

Usey95

@leviding @shixi-li 校对完成。

Usey95 · 2019-06-10T10:07:06Z

TODO1/typescript-3-0-the-unknown-type.md


-The main difference between `unknown` and `any` is that `unknown` is much less permissive than `any`: we have to do some form of checking before performing most operations on values of type `unknown`, whereas we don't have to do any checks before performing operations on values of type `any`.
+`unknown` 和 `any` 的主要区别是 `unknown` 类型会更佳严格：在对 `unknown` 类型的值执行大多数操作之前，我们必须进行某种形式的检查。而在对 `any` 类型的值执行操作之前，我们不必进行任何检查。


"更佳严格" ==> "更加严格"

Usey95 · 2019-06-10T10:32:32Z

TODO1/typescript-3-0-the-unknown-type.md


-The `any` type has been in TypeScript since the first release in 2012. It represents all possible JavaScript values --- primitives, objects, arrays, functions, errors, symbols, what have you.
+自从 TypeScript 在 2012 年发布第一个版本以来 `any` 类型就一直存在。它代表所有可能的 JavaScript 值 — 原语，对象，数组，函数，错误，符号，以及任何你可能定义的值。


原语 ==> 基本类型
Error，Symbol建议不译首字母大写

Usey95 · 2019-06-10T10:52:35Z

TODO1/typescript-3-0-the-unknown-type.md


-In TypeScript, every type is assignable to `any`. This makes `any` a [*top type*](https://en.wikipedia.org/wiki/Top_type) (also known as a *universal supertype*) of the type system.
+在 TypeScript 中，每个类型都可以被定义为 `any` 类型。every type is assignable to `any`. 这让 `any` 类型成为了类型系统的 [*顶级类型*](https://en.wikipedia.org/wiki/Top_type) (也被称作 *全局超级类型*)。


删除原文"every type is assignable to any."
==> 任何类型都可以被归为 any 类型。

Usey95 · 2019-06-10T10:58:53Z

TODO1/typescript-3-0-the-unknown-type.md


-Just like all types are assignable to `any`, all types are assignable to `unknown`. This makes `unknown` another top type of TypeScript's type system (the other one being `any`).
+就像所有类型都可以被定义为 `any`，所有类型也都可以被定义为 `unknown`。这使得 `unknown` 成为 TypeScript 类型系统的另一种顶级类型（另一种是  `any`）。


被定义为 ==> 被归为

Usey95 · 2019-06-10T11:16:29Z

TODO1/typescript-3-0-the-unknown-type.md


-Let's now look at how the `unknown` type is treated within union types. In the next section, we'll also look at intersection types.
+现在让我们看一下在 union 类型中如何处理`unknown`类型。在下一节中，我们还将了解交叉类型。


union类型 => 联合类型

Usey95 · 2019-06-10T11:23:46Z

TODO1/typescript-3-0-the-unknown-type.md


 ```ts
 type UnionType5 = unknown | any;  // any
 ```

-So why does `unknown` absorb every type (aside from `any`)? Let's think about the `unknown | string` example. This type represents all values that are assignable to type `unknown` plus those that are assignable to type `string`. As we've learned before, all types are assignable to `unknown`. This includes all strings, and therefore, `unknown | string` represents the same set of values as `unknown` itself. Hence, the compiler can simplify the union type to `unknown`.
+所以为什么 `unknown` 可以吸收任何类型（`any` 类型除外）？让我们来想想 `unknown | string` 这个例子。这个类型表示可以被定义为 `unknown` 类型的所有的值加上可以被定义成 `string` 类型的所有的值。就像我们之前了解到的，所有类型的值都可以被定义为 `unknown` 类型，其中也包括了所有的 `string` 类型，也就是说因此，`unknown | string` 就是表示和 `unknown` 类型本身相同的值集。因此，编译器可以将联合类型简化为 `unknown` 类型。


『这个类型可以表示任何 unkown 类型或者 string 类型的值』
『也就是说因此』=> 『因此』

同意校对的说法，更加简洁

Usey95 · 2019-06-10T11:26:32Z

TODO1/typescript-3-0-the-unknown-type.md


 -   `===`
 -   `==`
 -   `!==`
 -   `!=`

-If you want to use any other operators on a value typed as `unknown`, you have to narrow the type first (or force the compiler to trust you using a type assertion).
+如果要对类型为 `unknown` 的值使用任何其他运算符，则必须先指定类型（或强制编译器使用类型断言信任您）。


『或强制编译器使用类型断言信任您』 => 『或使用类型断言强制编译器信任你』

Usey95 · 2019-06-10T11:27:52Z

TODO1/typescript-3-0-the-unknown-type.md


-Let's assume we want to write a function that reads a value from `localStorage`and deserializes it as JSON. If the item doesn't exist or isn't valid JSON, the function should return an error result; otherwise, it should deserialize and return the value.
+假设我们要编写一个从 `localStorage` 读取值并将其反序列化为 JSON 的函数。如果该项不存在或者是无效 JSON，则该函数应返回错误结果；否则，它应该反序列化并返回值。


分号改逗号

Usey95 · 2019-06-10T11:31:14Z

TODO1/typescript-3-0-the-unknown-type.md


-1. The value `null` is a valid JSON value. Therefore, we would not be able to distinguish whether we deserialized the value `null` or whether the entire operation failed because of a missing item or a syntax error.
-2. If we were to return `null` from the function, we could not return the error at the same time. Therefore, callers of our function would not know why the operation failed.
+1. `null` 值是一个无效的 JSON 值。因此，我们无法区分是对值 `null` 进行了反序列化，还是由于缺少参数或语法错误而导致整个操作失败。


『无效』=> 『有效』

Usey95 · 2019-06-10T11:38:41Z

TODO1/typescript-3-0-the-unknown-type.md


-For the sake of completeness, a more sophisticated alternative to this approach is to use [typed decoders](https://dev.to/joanllenas/decoding-json-with-typescript-1jjc) for safe JSON parsing. A decoder lets us specify the expected schema of the value we want to deserialize. If the persisted JSON turns out not to match that schema, the decoding will fail in a well-defined manner. That way, our function always returns either a valid or a failed decoding result and we could eliminate the `unknown` type altogether.
+为了返回完整性，使用这种方法的更复杂的替代方案[类型解码器](https://dev.to/joanllenas/decoding-json-with-typescript-1jjc) 来用于安全的 JSON 解析。解码器需要我们指定要反序列化的值的预期数据结构。如果持久化的JSON结果与该数据结构不匹配，则解码将以明确定义的方式失败。这样，我们的函数总是返回有效或失败的解码结果，我们可以完全消除`unknown`类型。


『为了返回完整性，使用这种方法的更复杂的替代方案』=> 『为了完整性，这种方法的梗成熟的替代方案是使用类型解码器进行安全的 JSON 解析。』
『我们可以完全消除unknown类型』 => 『就不再需要 unknown 类型了。』

smilemuffie

译者可以在第一位校对者的建议上改一下哦，简洁化下一些语句，翻译的很棒，校对的也很棒

smilemuffie · 2019-06-11T08:44:00Z

TODO1/typescript-3-0-the-unknown-type.md

@@ -1,27 +1,27 @@
-> * 原文地址：[TypeScript 3.0: The unknown Type](https://mariusschulz.com/blog/typescript-3-0-the-unknown-type)
+> * 原文地址：[TypeScript 3.0: The unknown Type](https://mariusschulz.com/blog/typescript-3-0-the-unknown-type)
 > * 原文作者：[Marius Schulz](https://mariusschulz.com) 
 > * 译文出自：[掘金翻译计划](https://github.com/xitu/gold-miner)
 > * 本文永久链接：[https://github.com/xitu/gold-miner/blob/master/TODO1/typescript-3-0-the-unknown-type.md](https://github.com/xitu/gold-miner/blob/master/TODO1/typescript-3-0-the-unknown-type.md)
 > * 译者：
 > * 校对者


smilemuffie

译者，校对者的 github 链接都漏了哦

smilemuffie · 2019-06-11T08:51:10Z

TODO1/typescript-3-0-the-unknown-type.md


 ```ts
 type UnionType5 = unknown | any;  // any
 ```

-So why does `unknown` absorb every type (aside from `any`)? Let's think about the `unknown | string` example. This type represents all values that are assignable to type `unknown` plus those that are assignable to type `string`. As we've learned before, all types are assignable to `unknown`. This includes all strings, and therefore, `unknown | string` represents the same set of values as `unknown` itself. Hence, the compiler can simplify the union type to `unknown`.
+所以为什么 `unknown` 可以吸收任何类型（`any` 类型除外）？让我们来想想 `unknown | string` 这个例子。这个类型表示可以被定义为 `unknown` 类型的所有的值加上可以被定义成 `string` 类型的所有的值。就像我们之前了解到的，所有类型的值都可以被定义为 `unknown` 类型，其中也包括了所有的 `string` 类型，也就是说因此，`unknown | string` 就是表示和 `unknown` 类型本身相同的值集。因此，编译器可以将联合类型简化为 `unknown` 类型。


同意校对的说法，更加简洁

smilemuffie · 2019-06-11T08:55:42Z

校对完毕 @shixi-li @leviding @Usey95 翻译者校对者记得添加github链接信息哦

leviding · 2019-06-13T10:19:25Z

@shixi-li 有空的时候可以修改啦

shixi-li · 2019-06-14T03:48:59Z

@Usey95 @smilemuffie 非常感谢两位的校正。

@fanyijihua @leviding 修改完毕。

leviding

各位辛苦啦，译者 @shixi-li 看下最新的一个 commit，我修改了一些细节问题，麻烦注意一下 ⚠️

leviding · 2019-06-14T07:30:40Z

@shixi-li 已经 merge 啦~ 快快麻溜发布到掘金然后给我发下链接，方便及时添加积分哟。

掘金翻译计划有自己的知乎专栏，你也可以投稿哈，推荐使用一个好用的插件。
专栏地址：https://zhuanlan.zhihu.com/juejinfanyi

李是希 and others added 14 commits March 23, 2019 01:02

翻译初步完成

61271a9

初次自校

9048dd6

update

b82e6ef

update

e62f73e

根据Reaper622校对意见修改

db2f8d3

根据kasheemlew意见校正，以及调整字句

35a6bfe

update

655e11b

update

333666e

update

8ae2a55

Update understanding-a-performance-issue-with-polymorphic-json-data.md

381e55a

Merge branch 'master' of https://github.com/shixi-li/gold-miner

10b6ae4

Merge remote-tracking branch 'upstream/master'

048f11a

Merge remote-tracking branch 'upstream/master'

b3efaea

初步翻译完成

ba3b33c

fanyijihua added the 校对认领 label Jun 9, 2019

fanyijihua mentioned this pull request Jun 9, 2019

TypeScript 3.0: unknown 类型 #5863

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lsvih changed the title ~~Translation/typescript 3 0 the unknown type~~ TypeScript 3.0: unknown 类型 Jun 9, 2019

lsvih added the 前端 label Jun 9, 2019

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shixi.li added 2 commits June 14, 2019 11:30

根据校对意见修改

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TypeScript 3.0: unknown 类型 #5929

TypeScript 3.0: unknown 类型 #5929

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leviding commented Jun 14, 2019


		The main difference between `unknown` and `any` is that `unknown` is much less permissive than `any`: we have to do some form of checking before performing most operations on values of type `unknown`, whereas we don't have to do any checks before performing operations on values of type `any`.
		`unknown` 和 `any` 的主要区别是 `unknown` 类型会更佳严格：在对 `unknown` 类型的值执行大多数操作之前，我们必须进行某种形式的检查。而在对 `any` 类型的值执行操作之前，我们不必进行任何检查。


		The `any` type has been in TypeScript since the first release in 2012. It represents all possible JavaScript values --- primitives, objects, arrays, functions, errors, symbols, what have you.
		自从 TypeScript 在 2012 年发布第一个版本以来 `any` 类型就一直存在。它代表所有可能的 JavaScript 值 — 原语，对象，数组，函数，错误，符号，以及任何你可能定义的值。


		In TypeScript, every type is assignable to `any`. This makes `any` a [top type](https://en.wikipedia.org/wiki/Top_type) (also known as a universal supertype) of the type system.
		在 TypeScript 中，每个类型都可以被定义为 `any` 类型。every type is assignable to `any`. 这让 `any` 类型成为了类型系统的 [顶级类型](https://en.wikipedia.org/wiki/Top_type) (也被称作全局超级类型)。


		Just like all types are assignable to `any`, all types are assignable to `unknown`. This makes `unknown` another top type of TypeScript's type system (the other one being `any`).
		就像所有类型都可以被定义为 `any`，所有类型也都可以被定义为 `unknown`。这使得 `unknown` 成为 TypeScript 类型系统的另一种顶级类型（另一种是 `any`）。


		Let's now look at how the `unknown` type is treated within union types. In the next section, we'll also look at intersection types.
		现在让我们看一下在 union 类型中如何处理`unknown`类型。在下一节中，我们还将了解交叉类型。


		Let's assume we want to write a function that reads a value from `localStorage`and deserializes it as JSON. If the item doesn't exist or isn't valid JSON, the function should return an error result; otherwise, it should deserialize and return the value.
		假设我们要编写一个从 `localStorage` 读取值并将其反序列化为 JSON 的函数。如果该项不存在或者是无效 JSON，则该函数应返回错误结果；否则，它应该反序列化并返回值。


		For the sake of completeness, a more sophisticated alternative to this approach is to use [typed decoders](https://dev.to/joanllenas/decoding-json-with-typescript-1jjc) for safe JSON parsing. A decoder lets us specify the expected schema of the value we want to deserialize. If the persisted JSON turns out not to match that schema, the decoding will fail in a well-defined manner. That way, our function always returns either a valid or a failed decoding result and we could eliminate the `unknown` type altogether.
		为了返回完整性，使用这种方法的更复杂的替代方案[类型解码器](https://dev.to/joanllenas/decoding-json-with-typescript-1jjc) 来用于安全的 JSON 解析。解码器需要我们指定要反序列化的值的预期数据结构。如果持久化的JSON结果与该数据结构不匹配，则解码将以明确定义的方式失败。这样，我们的函数总是返回有效或失败的解码结果，我们可以完全消除`unknown`类型。

TypeScript 3.0: unknown 类型 #5929

TypeScript 3.0: unknown 类型 #5929

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shixi-li commented Jun 9, 2019

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