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TS | ts-utils

interface ArrayLike<T> {
  readonly length: number;
  readonly [n: number]: T;
}

Partial​

  • Make all properties in T optional
  • 将 T 中的所有属性设置为可选
type Partial<T> = {
  [P in keyof T]?: T[P];
};

例子

type obj = {
  name: string;
  age: number;
};

const o1: Partial<obj> = {
  name: "YZJ",
};

Required​

  • Make all properties in T required
  • 使 T 中的所有属性都是必需的
type Required<T> = {
  [P in keyof T]-?: T[P];
};

例子

const o2: Required<obj> = {
  name: "YZJ",
  age: 26,
};

Readonly​

  • Make all properties in T readonly
  • 使 T 中所有的属性都是可读
type Readonly<T> = {
  readonly [P in keyof T]: T[P];
};

例子

const o3: Readonly<obj> = {
  name: "YZJ",
  age: 26,
};

// 修改 报错  o3 内的属性只读 无法进行修改
o3.age = 111;

错误信息

Pick​

  • From T, pick a set of properties whose keys are in the union K
  • 从 T 中，选择一组键位于并集 K 中的属性
type Pick<T, K extends keyof T> = {
  [P in K]: T[P];
};

Record​

  • Construct a type with a set of properties K of type T
  • 构造一个具有一组类型为 T 的属性 K 的类型
type Record<K extends keyof any, T> = {
  [P in K]: T;
};

例子

type keys = "a" | "b" | "c";
const a: Record<keys, number> = {
  a: 2,
  b: 3,
  c: 2,
};

Exclude​

  • Exclude from T those types that are assignable to U
  • 从 T 中排除那些可分配给 U 的类型
type Exclude<T, U> = T extends U ? never : T;

Extract​

  • Extract from T those types that are assignable to U
  • 从 T 中提取可分配给 U 的类型
type Extract<T, U> = T extends U ? T : never;

Omit​

  • Construct a type with the properties of T except for those in type K.
  • 构造一个属性为 T 的类型，但类型 K 中的属性除外
type Omit<T, K extends keyof any> = Pick<T, Exclude<keyof T, K>>;

NonNullable​

  • Exclude null and undefined from T
  • 从 T 中排除 null 和未定义
type NonNullable<T> = T extends null | undefined ? never : T;

Parameters​

  • Obtain the parameters of a function type in a tuple
  • 获取元组中函数类型的参数
type Parameters<T extends (...args: any) => any> = T extends (
  ...args: infer P
) => any
  ? P
  : never;

ConstructorParameters​

  • Obtain the parameters of a constructor function type in a tuple
  • 获取元组中构造函数类型的参数
  type ConstructorParameters<T extends abstract new (...args: any) => any> = T extends abstract new (...args: infer P) => any ? P : never;

ReturnType​

  • Obtain the return type of a function type
  • 获取函数类型的返回类型
type ReturnType<T extends (...args: any) => any> = T extends (
  ...args: any
) => infer R
  ? R
  : any;

InstanceType​

  • Obtain the return type of a constructor function type
  • 获取构造函数类型的返回类型
  type InstanceType<T extends abstract new (...args: any) => any> = T extends abstract new (...args: any) => infer R ? R : any;

Uppercase​

  • Convert string literal type to uppercase
  • 将字符串文字类型转换为大写
type Uppercase<S extends string> = intrinsic;

Lowercase​

  • Convert string literal type to lowercase
  • 将字符串文字类型转换为小写
type Lowercase<S extends string> = intrinsic;

Capitalize​

  • Convert first character of string literal type to uppercase
  • 将字符串文字类型的第一个字符转换为大写
type Capitalize<S extends string> = intrinsic;

Uncapitalize​

  • Convert first character of string literal type to lowercase
  • 将字符串文字类型的第一个字符转换为小写
type Uncapitalize<S extends string> = intrinsic;