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内置类型 ​

Partial ​

将属性变为可选。

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

Required ​

将属性变为必选。通过 - 移除修饰符 ?。默认为 + 号。

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

Readonly ​

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

Writeable ​

同理，使用 - 移除 readonly 修饰符。

typescript
type Writeable<T> = { 
  -readonly [P in keyof T]: T[P] 
};

Record ​

对象形式

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

Exclude ​

排除

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

Extract ​

选取、取出。

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

Omit ​

排除部分属性

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

Pick ​

选取部分属性

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

NonNullable ​

排除 null 和 undefined

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

Parameters ​

参数类型

typescript
type Parameters<T extends (...args: any) => any> = T extends (...args: infer P) => any ? P : never;

ReturnType ​

函数返回值类型

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

ConstructorParameters ​

构造函数参数类型

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

InstanceType ​

类的实例类型

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

内置 ​

typescript
// 全部大写
type Uppercase<S extends string> = intrinsic;
// 全部小写
type Lowercase<S extends string> = intrinsic;
// 首字母大写
type Capitalize<S extends string> = intrinsic;
// 首字母小写
type Uncapitalize<S extends string> = intrinsic;

Equals ​

类型判断

typescript
type Equals<X, Y> =
  (<T>() => T extends X ? 1 : 2) extends
  (<T>() => T extends Y ? 1 : 2) ? true : false;