第六十一周总结——重拾ts类型体操

重拾ts类型体操

匹配模式做提取

1. 数组类型

• 提取数组第一个元素的类型

type GetFirst<Arr extends unknown[]> = Arr extends [infer First, ...unknown[]] ? First : never;

• 提取数组的最后一个元素的类型

type GetLast<Arr extends unknown[]> = Arr extends [...unknown[],infer Last] ? Last : never;

• 去掉数组最后一个元素的类型

type PopArr<Arr extends unknown[]> = Arr extends [] ? [] : Arr extends [...infer Result,unknown] ? Result : never;

• 去掉数组第一个元素的类型

type ShiftArr<Arr extends unknown[]> = Arr extends [] ? [] : Arr extends [unknown,...infer Result] ? Result : never;

2. 字符串类型

• 判断字符串是否以某个前缀开始

type StartWith<Str extends string, Start extends string> = Str extends `${Start}${string}` ? true : false;

• 字符串替换

type ReplaceStr<
  Str extends string,
  From extends string,
  To extends string
> = Str extends `${infer Prefix}${From}${infer Suffix}` ?
    ReplaceStr<`${Prefix}${To}${Suffix}`,From,To> : Str

• 递归去除字符串中的右侧空格

type TrimStringRight<Str extends string> = Str extends `${infer Result}${' '}` ? TrimStringRight<Result> : Str;

• 递归去除字符串中的左侧空格

type TrimStringLeft<Str extends string> = Str extends `${' '}${infer Result}` ? TrimStringLeft<Result> : Str;

• 递归去除字符串中的左右侧空格

type TrimString<Str extends string> = Str extends `${' '}${infer Result}${' '}` ? TrimString<Result> : Str;

3. 函数

• 提取参数的类型

type FunctionArgs<Fn extends Function> = Fn extends (...args:infer Args) => unknown ? Args : never;

• 提取返回值

type FunctionResult<Fn extends Function> = Fn extends (...args:any[]) => infer Result ? Result : never;

• 提取函数中的this

type FunctionThis<Fn extends Function> = Fn extends (this:infer This,...args:unknown[])=>unknown ? This : never;

4. 构造器

• 匹配提取出实例对象

type GetInstanceType<Type extends new(...args:any[])=>any> = Type extends new(...args:any) => infer Result ? Result : never;
// 测试案例
interface Person{
  name: string
}
interface PersonConstructor{
  new(name:string):Person
}
type person = GetInstanceType<PersonConstructor>;

• 提取构造器的参数

type GetInstanceParam<Type extends new(...args:any[])=>any> = Type extends new(...args:infer Result) => unknown ? Result : never;
// 测试案例
interface Person{
  name: string
}
interface PersonConstructor{
  new(name:void):Person
}
type person = GetInstanceParam<PersonConstructor>;

5. 索引类型

• 提取ref的值的类型
  ts类型体操，提取ref的值的类型。

重新构造做变换

1. 数组类型的重新构造

• 向数组后面添加元素

type Push<Arr extends unknown[],Ele> = [...Arr,Ele];

• 向数组前面添加元素

type Shift<Ele, Arr extends unknown[]> = [Ele,...Arr];

• 合并只有两个元素的两个元组对应的元素

type Concat<One extends [unknown,unknown],Two extends [unknown,unknown]> = 
One extends [infer OneFirst, infer OneSecond] ?
  Two extends [infer TwoFirst, infer TwoSecond] ? [[OneFirst,OneSecond],[TwoFirst,TwoSecond]] : []
: []

• 合并只有任意个元素的两个元组对应的元素

type Concat<One extends unknown[],Two extends unknown[]> = 
One extends [infer OneFirst,...infer OneOther] ?
  Two extends [infer TwoFirst,...infer TwoOther] ? [[OneFirst,TwoFirst],...Concat<OneOther,TwoOther>] : []
: [];

2. 字符串的重新构造

• 将字符串第一个元素转换成大写

type StringFistToUp<Str extends string> = Str extends `${infer First}${infer Other}` ? `${Uppercase<First>}${Other}` : never

• 删除字符串中的某个字串

type DeleteString<Str extends string,Ele extends string> = 
Str extends `${infer Start}${Ele}${infer End}` ? DeleteString<`${Start}${End}`,Ele> : Str

• 函数类型的重新构造

type FunAddParam<Fn extends Function,Arg extends unknown> =
Fn extends (...args:infer Args)=>infer Result ? (...args:[...Args,Arg])=>Result : never

3. 索引类型重新构造

• 把索引类型的Key变成大写

type KeyUp<Obj extends Object> = {
  [Key in keyof Obj as Uppercase<Key & string>]:Obj[Key];
}

• Record，typescript内置了Record，用来创建索引类型。

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

• 将索引转换成只读

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

• 给索引添加可选修饰符

type toSelector<T> = {
  [P in keyof T]?: T[P]
}

• 去掉只读修饰符

type RemoveReadonly<T> = {
  -readonly [P in keyof T]: T[P]
}

• 去掉可选修饰符

type ClearSelector<T> = {
  [P in keyof T]-?: T[P]
}

• 对索引类型做过滤

type FilterValue<T extends Record<string,any>,valueType extends unknown> = {
  [Key in keyof T as T[Key] extends valueType ? Key : never]: T[Key]
}

递归复用做循环

1. Promise的递归调用

• 提取不确定层数的Promise中的value类型的高级类型

type PromiseValue<T> = 
T extends Promise<infer Value>?
  PromiseValue<Value>
: T
type promise = PromiseValue<Promise<Promise<Record<string,any>>>>

2. 数组类型的递归

• 不确定长度的元组反转

type ReverseArr<T extends Array<unknown>> = T extends [infer First,...infer Other] ? [...ReverseArr<Other>,First] : T;

• 寻找元组中是否存在某个元素

type IsEqual<A,B> = (A extends B ? true : false) & (B extends A ? true : false);
type Include<Arr extends unknown[],Ele> = 
Arr extends [infer First,...infer Other] ?
  IsEqual<First,Ele> extends true ? true : Include<Other,Ele>
: false;

• 删除元组中的某个元素

type RemoveArrItem<
  Arr extends unknown[],
  Item,
  Result extends unknown[] = []
> = Arr extends [infer First,...infer Other] ?
  IsEqual<Item,First> extends true ? RemoveArrItem<Other,Item,Result> : RemoveArrItem<Other,Item,[...Result,First]>
: Result
type IsEqual<A,B> = (A extends B ? true : false) & (B extends A ? true : false)

• 构建一个自定义长度的同一类别的数组

type BuildArr<
  Length extends number,
  Ele,
  Arr extends unknown[] = []
> = Arr['length'] extends Length ? Arr : BuildArr<Length,Ele,[...Arr,Ele]>

3. 字符串类型的递归

• 将字符串中的所用的指定字串替换成另一个字符串

type Replace<
  Str extends string,
  From extends string,
  To extends string
> = Str extends `${infer Start}${From}${infer End}` ? Replace<`${Start}${To}${End}`,From,To> : Str

• 将字符串的每个元素提取出来转换成联合类型

type StrType<Str extends string,Result = never> = Str extends `${infer First}${infer Other}` ? StrType<Other,Result|First> : Result

• 反转字符串类型

type ReverseString<Str extends string,Result extends string = ""> = Str extends `${infer First}${infer Other}` ? ReverseString<Other,`${Result}${First}`> : Result

4. 对象类型的递归(索引类型的递归)

-递归将所有层的索引都变成只读
错误代码，如果测试一下我们就会发现，递归没有进行下去。因为ts的类型只有被用到的时候才会被计算。这里只是给第一次的索引加上了只读，但是没有使用。所以不会进行计算，我们可以加一个Obj extends any让其计算。

type DeepReadonly<Obj extends Record<string,any>> = Obj extends any ? {
  readonly [Key in keyof Obj]: Obj[Key] extends Record<string,any> ? 
    Obj[Key] extends Function ? Obj[Key] : DeepReadonly<Obj[Key]>
  : Obj[Key]
} : never

数组长度做计算

1. 数组长度实现加减乘除

• 加

type BuildArray<
  Length extends number,
  Ele = unknown,
  Result extends unknown[] = []
> = Result['length'] extends Length ? Result : BuildArray<Length,Ele,[Ele,...Result]>
type Add<Arr extends unknown[],Result extends unknown[] = []> = Arr extends [infer Start extends number,...infer Other]
                                                          ? Add<Other,[...BuildArray<Start>,...Result]> : 
                                                          Result['length']
type s = Add<[1,2,3]>

• 减

type BuildArray<
  Length extends number,
  Ele = unknown,
  Result extends unknown[] = []
> = Result['length'] extends Length ? Result : BuildArray<Length,Ele,[Ele,...Result]>
type SubTract<Num1 extends number,Num2 extends number> = BuildArray<Num1> extends [...BuildArray<Num2>,...infer Result] ? Result['length'] : never

• 乘

type BuildArray<
  Length extends number,
  Ele = unknown,
  Result extends unknown[] = []
> = Result['length'] extends Length ? Result : BuildArray<Length,Ele,[Ele,...Result]>
type SubTract<Num1 extends number,Num2 extends number> = BuildArray<Num1> extends [...BuildArray<Num2>,...infer Result] ? Result['length'] : never

type Multiply<
  Num1 extends number,
  Num2 extends number,
  Result extends unknown[] = []
> = Num1 extends 0 ? Result['length'] : Multiply<SubTract<Num1,1>,Num2,[...Result,...BuildArray<Num2>]>

• 除

type BuildArray<
  Length extends number,
  Ele = unknown,
  Arr extends unknown[] = []
> = Arr['length'] extends Length ?
    Arr :
    BuildArray<Length,Ele,[...Arr,Ele]>
type Subtract<Num1 extends number, Num2 extends number> = BuildArray<Num1> extends [...arr1: BuildArray<Num2>, ...arr2: infer Rest] ?
Rest['length'] : never

type Divide<
  Num1 extends number,
  Num2 extends number,
  ResultArr extends unknown[] = []
> = Num1 extends 0 ?
    ResultArr['length'] :
    Divide<Subtract<Num1,Num2>,Num2,[unknown, ...ResultArr]>;
type divide = Divide<6,3>;

• 求字符串的长度的类型

type StrLen<
  Str extends string,
  ResultArr extends unknown[] = []
> = Str extends `${string}${infer Rest}`? 
  StrLen<Rest,[...ResultArr, unknown]>
: ResultArr['length'];
type str = StrLen<'123'>;

• 比较两个值的大小

type Than<
  Num1 extends number,
  Num2 extends number,
  Count extends unknown[] = []
> = Num1 extends Num2 ? false :
  Count['length'] extends Num2 ? true :
  Count['length'] extends Num1 ? false :
  Than<Num1,Num2,[unknown,...Count]>

• Fibonacci 数列的计算

type Fi<
  Left extends unknown[],
  Right extends unknown[],
  Num extends number,
  Idx extends unknown[] = [],
  > = Idx['length'] extends Num ? Right['length'] : Fi<Right,[...Left,...Right],Num,[...Idx,unknown]>

type Fib<Num extends number> = Fi<[],[1],Num,[1]>

联合分散可化简

1. 将联合类型的字符串_去点，并将_后的第一个字母大写

type Tool<Str extends string> = Str extends `${infer First}_${infer Start}${infer End}` ? Tool<`${First}${Uppercase<Start>}${End}`> : Str
type item = Tool<'aa_bb_cc_dd'>;

2. 判断联合类型

type Tool<A, B = A> =
A extends A?
  [B] extends [A] ? false : true
: never

3. BEM
   BEM是css命名规范

type bemResult = BEM<'guang', ['aaa', 'bbb'], ['warning', 'success']>;
//会转换成
guang__aaa--warning guang__bbb--success

type BEM<Ele1 extends string,Ele2 extends string[],Ele3 extends string[]> = `${Ele1}__${Ele2[number]}--${Ele3[number]}`

4. AllCombinations

type Combination<A extends string, B extends string> =
    | A
    | B
    | `${A}${B}`
    | `${B}${A}`;
type AllCombinations<A extends string, B extends string = A> = 
A extends A
    ? Combination<A, AllCombinations<Exclude<B, A>>>
    : never;
type all = AllCombinations<'A' | 'B' | 'C'>;

特殊类型要记清

1. IsEqual

type IsEqual<A,B> = (<T>()=>T extends A ? 1 : 2) extends (<T>()=>T extends B ? 1 : 2) ? true : false

2. 几个条件类型的特殊情况

• 联合类型作为类型参数在条件类型左边的时候，会把每个类型单独传入做计算，并把结果合并成联合类型。

type Test<T> = T extends number ? 1 : 2;
type res = Test<1 | 'a'>;//type res = 1 | 2

• boolean也是联合类型，是false | true。

type Test<T> = T extends true ? 1 : 2;
type res = Test<boolean>;//type res = false | true

• any类型如果在条件类型的左边，则返回trueType和falseType的联合类型。

type Test<T> = T extends true ? 1 : 2;
type res = Test<any>;//type res = 1 | 2

• 当条件类型的左侧是never的时候直接返回never。

type Test<T> = T extends true ? 1 : 2;
type res = Test<never>;//type res = never

内置高级类型

1. Parameters-用来提取函数参数的类型

type Parameters<T extends (...args: any) => any> = T extends (...args: infer P) => any ? P : any;

2. ResultType-用来提取函数的返回值类型

type ReturnType<T extends (...args: any) => any> = T extends (...args: any) => infer R ? R : any;

3. ConstructorParameters-用来提取构造器的参数类型

type ConstructorParameters<T extends abstract new (...args: any) => any> = T extends abstract new (...args: infer P) => any ? P : never;

4. InstanceType-用来提取构造器的返回值类型

type InstanceType<T extends abstract new (...args: any) => any> = T extends abstract new (...args: any) => infer R ? R : any;

5. Partial-把索引类型变成可选类型

type Partial<T> = {
    [P in keyof T]?: T[P];
};

6. Required-把可选的索引类型变成必选类型

type Required<T> = {
    [P in keyof T]-?: T[P];
};

7. Readonly-把索引类型变成只读类型

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

8. Pick-对索引进行修改和过滤,保留对应的索引

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

9. Record-用来创建索引类型

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

10. Exclude-用来删除联合类型的一部分

type Exclude<T, U> = T extends U ? never : T;

11. Extract-用来保留联合类型的一部分

type Extract<T, U> = T extends U ? T : never;

12. Omit-和Pick相反，去掉对应的索引

type Omit<T, K extends keyof any> = Pick<T, Exclude<keyof T, K>>;

13. Awaited-用来获取Promise的ValueType的类型

type Awaited<T> =
    T extends null | undefined
        ? T 
        : T extends object & { then(onfulfilled: infer F): any }
            ? F extends ((value: infer V, ...args: any) => any)
                ? Awaited<V>
                : never 
            : T;

14. NonNullable-用来判断是否为非空类型

type NonNullable<T> = T extends null | undefined ? never : T;

15. ThisParameterType-函数里可以调用 this，这个 this 的类型也可以约束。

type ThisParameterType<T> = 
    T extends (this: infer U, ...args: any[]) => any 
        ? U 
        : unknown;

16. OmitThisParameter-用来提取this

type OmitThisParameter<T> = 
    unknown extends ThisParameterType<T> 
        ? T 
        : T extends (...args: infer A) => infer R 
            ? (...args: A) => R 
            : T;