日刷|课程|TS类型体操

node_modules/typescript/lib/lib.es5.d.ts
官网：https://www.typescriptlang.org/docs/handbook/utility-types.html

同学笔记：
TS常用关键字和工具范型梳理 https://snowwolf2.yuque.com/staff-rmd8eh/gmflbs/ngchuc
TS Utils https://snowwolf2.yuque.com/staff-rmd8eh/gmflbs/ra4fve#ekml3

https://github.com/type-challenges/type-challenges

Pick

type MyPick <T, K extends keyof T> = {
    [P in K]: T[P];
};

用法

https://www.typescriptlang.org/docs/handbook/utility-types.html#picktype-keys

解析：

function myPick (todo, keys) {
    let ans = {};
    for (let key of keys) {
        if (key in todo) {
            ans[key] = todo[key];
        }
    }
    return ans;
}

涉及到的知识点

:::success 1.返回一个对象
2.遍历foreach mapped
https://www.typescriptlang.org/docs/handbook/2/mapped-types.html
3.todo[key] 取值indexed
https://www.typescriptlang.org/docs/handbook/2/indexed-access-types.html
4.看看key在不在todo里面
1.keyof lookup
https://www.typescriptlang.org/docs/handbook/release-notes/typescript-2-1.html#keyof-and-lookup-types
2.extends条件约束
https://www.typescriptlang.org/docs/handbook/2/generics.html#generic-constraints :::

Readonly

type MyReadonly<T> = {
    readonly [P in keyof T]: T[P];
}

用法

https://www.typescriptlang.org/docs/handbook/utility-types.html#readonlytype

解析：

function myReadonly(todo) {
    let ans = {};
    for (let key in todo) {
        ans[`readonly ${key}`] = todo[key];
    }
    return ans;
}

涉及到的知识点

:::success 1.返回一个对象
2.遍历对象
2.1in
2.2mapped keyof
2.3lookup
3.添加readonly关键字 【新知识】
4.通过key获取对应的值 :::

Tuple to Object

解析case：

1. typeof 获取类型
2. 字面量类型 ， ex: const
3. @ts-expect-error 注释

解析题目：

1. 返回一个对象
2. 遍历数组 P in T[number]

type TupleToObject<T extends readonly (number | string | symbol)[]> = {
    [P in T[number]]: P;
}