内置工具类型

  1// 内置工具类型完整目录（行为均经实测验证）
  2
  3interface User {
  4  id: number;
  5  name: string;
  6  email: string;
  7  age: number;
  8}
  9
 10// ==================== 对象变换 ====================
 11type P = Partial<User>;                        // 全部可选
 12type R = Required<P>;                          // 全部必需
 13type RO = Readonly<User>;                      // 全部只读
 14type Picked = Pick<User, "id" | "name">;       // 只保留指定键
 15type Omitted = Omit<User, "email">;            // 排除指定键
 16type Rec = Record<"a" | "b", number>;          // { a: number; b: number }
 17
 18// ==================== 联合变换 ====================
 19type U = Exclude<"a" | "b" | "c", "a">;        // "b" | "c"
 20type I = Extract<"a" | "b" | "c", "a" | "b">;  // "a" | "b"
 21type NN = NonNullable<string | null | undefined>;   // string
 22
 23// ==================== 函数变换 ====================
 24type Fn = (this: { id: number }, a: string, b: number) => boolean;
 25
 26type Ret = ReturnType<Fn>;                     // boolean
 27type Params = Parameters<Fn>;                  // [string, number]
 28type ThisT = ThisParameterType<Fn>;            // { id: number }
 29type NoThis = OmitThisParameter<Fn>;           // (a: string, b: number) => boolean
 30
 31// 构造函数相关
 32class Point { constructor(public x: number, public y: number) {} }
 33type CtorParams = ConstructorParameters<typeof Point>;   // [number, number]
 34type Inst = InstanceType<typeof Point>;                  // Point
 35
 36// ==================== Promise ====================
 37type A1 = Awaited<Promise<string>>;                  // string
 38type A2 = Awaited<Promise<Promise<number>>>;         // number（递归）
 39type A3 = Awaited<string | Promise<number>>;         // string | number
 40
 41// ==================== 字符串 ====================
 42type S1 = Uppercase<"a">;      // "A"
 43type S2 = Lowercase<"A">;      // "a"
 44type S3 = Capitalize<"ab">;    // "Ab"
 45type S4 = Uncapitalize<"Ab">;  // "ab"
 46
 47// ==================== 组合出项目专用工具 ====================
 48
 49// 把某个键变成可选
 50type PartialBy<T, K extends keyof T> = Omit<T, K> & Partial<Pick<T, K>>;
 51
 52// 把某个键变成必需
 53type RequiredBy<T, K extends keyof T> = Omit<T, K> & Required<Pick<T, K>>;
 54
 55// 只改一个键的类型
 56type Override<T, K extends keyof T, V> = Omit<T, K> & { [P in K]: V };
 57
 58// 深度 Partial
 59type DeepPartial<T> = {
 60  [K in keyof T]?: T[K] extends object ? DeepPartial<T[K]> : T[K];
 61};
 62
 63// 深度 Readonly
 64type DeepReadonly<T> = {
 65  readonly [K in keyof T]: T[K] extends object ? DeepReadonly<T[K]> : T[K];
 66};
 67
 68// 至少一个键必需（互斥或）
 69type AtLeastOne<T, K extends keyof T = keyof T> = Omit<T, K> &
 70  { [P in K]: Required<Pick<T, P>> & Partial<Record<Exclude<K, P>, never>> }[K];
 71
 72// 从联合里挑出函数的返回类型
 73type UnionReturn<T> = T extends (...args: never[]) => infer R ? R : never;
 74
 75// 把联合转成交叉
 76type UnionToIntersection<U> =
 77  (U extends unknown ? (x: U) => void : never) extends (x: infer I) => void ? I : never;
 78
 79// 取出值为某类型的键
 80type KeysOfType<T, V> = { [K in keyof T]: T[K] extends V ? K : never }[keyof T];
 81
 82// ==================== 验证 ====================
 83
 84const partial: P = { id: 1 };
 85const required: R = { id: 1, name: "a", email: "b", age: 1 };
 86const picked: Picked = { id: 1, name: "a" };
 87const omitted: Omitted = { id: 1, name: "a", age: 1 };
 88const rec: Rec = { a: 1, b: 2 };
 89const excl: U = "b";
 90const extr: I = "a";
 91const nonNull: NN = "s";
 92const ret: Ret = true;
 93const params: Params = ["s", 1];
 94const thisT: ThisT = { id: 1 };
 95const noThis: NoThis = (a: string, b: number) => a.length > b;
 96const ctorParams: CtorParams = [1, 2];
 97const inst: Inst = new Point(1, 2);
 98const a1: A1 = "s";
 99const a2: A2 = 1;
100const a3: A3 = "s";
101const s1: S1 = "A";
102const s2: S2 = "a";
103const s3: S3 = "Ab";
104const s4: S4 = "ab";
105
106const optEmail: PartialBy<User, "email"> = { id: 1, name: "a", age: 1 };
107const reqEmail: RequiredBy<P, "email"> = { id: 1, email: "b" };
108const strId: Override<User, "id", string> = { id: "1", name: "a", email: "b", age: 1 };
109const deep: DeepPartial<{ a: { b: { c: number } } }> = { a: { b: {} } };
110const deepRo: DeepReadonly<{ a: { b: number } }> = { a: { b: 1 } };
111const atLeast: AtLeastOne<{ a: number; b: string }> = { a: 1 };
112const unionRet: UnionReturn<() => string> = "s";
113const unionInter: UnionToIntersection<{ a: 1 } | { b: 2 }> = { a: 1, b: 2 };
114const keysOfType: KeysOfType<User, string> = "name";   // "name" | "email"
115
116console.log(partial, required, picked, omitted, rec, excl, extr, nonNull, ret, params);
117console.log(thisT, noThis, ctorParams, inst, a1, a2, a3, s1, s2, s3, s4);
118console.log(optEmail, reqEmail, strId, deep, deepRo, atLeast, unionRet, unionInter, keysOfType);

1{ id: 1 } [Function: noThis] [ 1, 2 ] Point { x: 1, y: 2 } s 1 s A a Ab ab
2{ id: 1, name: 'a', age: 1 } { id: 1, email: 'b' } { id: '1', name: 'a', email: 'b', age: 1 } { a: { b: {} } } { a: { b: 1 } } { a: 1 } s { a: 1, b: 2 } name

1type Fn = (this: { id: number }, a: string, b: number) => boolean;
2
3type ThisT = ThisParameterType<Fn>;     // { id: number }
4type NoThis = OmitThisParameter<Fn>;    // (a: string, b: number) => boolean

1Awaited<Promise<string>>              // string
2Awaited<Promise<Promise<number>>>     // number（递归）
3Awaited<string | Promise<number>>     // string | number

1type PartialBy<T, K extends keyof T> = Omit<T, K> & Partial<Pick<T, K>>;

1type RequiredBy<T, K extends keyof T> = Omit<T, K> & Required<Pick<T, K>>;

1type Override<T, K extends keyof T, V> = Omit<T, K> & { [P in K]: V };

1type DeepPartial<T> = {
2  [K in keyof T]?: T[K] extends object ? DeepPartial<T[K]> : T[K];
3};
4
5type DeepReadonly<T> = {
6  readonly [K in keyof T]: T[K] extends object ? DeepReadonly<T[K]> : T[K];
7};

1type AtLeastOne<T, K extends keyof T = keyof T> = Omit<T, K> &
2  { [P in K]: Required<Pick<T, P>> & Partial<Record<Exclude<K, P>, never>> }[K];

1type KeysOfType<T, V> = { [K in keyof T]: T[K] extends V ? K : never }[keyof T];

1type UnionToIntersection<U> =
2  (U extends unknown ? (x: U) => void : never) extends (x: infer I) => void ? I : never;

1# macOS ARM
2node_modules/@typescript/typescript-darwin-arm64/lib/lib.es5.d.ts