feat: translate Indexed Access Types.md in zh-CN

[EnochGao]

translate Indexed Access Types.md in zh-CN

[github-actions]

Thanks for the PR!

This section of the codebase is owned by @Kingwl - if they write a comment saying "LGTM" then it will be merged.

[github-actions]

Translation of Indexed Access Types.md

---

title: Index access type
layout: docs
permalink: /zh/docs/handbook/2/indexed-access-types.html

oneline: "Use Type['a'] syntax to get a subset of a type"

We can use Index access type to find another type of specific property:

type Person = { age: number; name: string; alive: boolean };
type Age = Person["age"];
//   ^?

The type being indexed is itself a type, so it is perfectly possible to use union,keyof or other types:

type Person = { age: number; name: string; alive: boolean };
// ---cut---
type I1 = Person["age" | "name"];
//   ^?

type I2 = Person[keyof Person];
//   ^?

type AliveOrName = "alive" | "name";
type I3 = Person[AliveOrName];
//   ^?

If you try to index a property that doesn't exist, you'll even see an error:

// @errors: 2339
type Person = { age: number; name: string; alive: boolean };
// ---cut---
type I1 = Person["alve"];

Another example of using an arbitrary type of index is using number to get the type of the array element. We can relate it to typeof Used together, it is convenient to get the type of array literal elements:

const MyArray = [
  { name: "Alice", age: 15 },
  { name: "Bob", age: 23 },
  { name: "Eve", age: 38 },
];

type Person = typeof MyArray[number];
//   ^?
type Age = typeof MyArray[number]["age"];
//   ^?
// Or
type Age2 = Person["age"];
//   ^?

Indexes can only function on types above, which means they cannot be used const to establish a variable reference:

// @errors: 2538 2749
type Person = { age: number; name: string; alive: boolean };
// ---cut---
const key = "age";
type Age = Person[key];

However, you can use type aliases for similar refactoring:

type Person = { age: number; name: string; alive: boolean };
// ---cut---
type key = "age";
type Age = Person[key];

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[EnochGao]

@Kingwl 麻烦处理一下中文相关的翻译吧，我看积累好多了