TypeScript Generics & Promise All In One

TypeScript Generics & Promise All In One

TypeScript 泛型 & Promise All In One

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/// <reference no-default-lib="true"/>


interface PromiseConstructor {
    /**
     * A reference to the prototype.
     */
    readonly prototype: Promise<any>;

    /**
     * Creates a new Promise.
     * @param executor A callback used to initialize the promise. This callback is passed two arguments:
     * a resolve callback used to resolve the promise with a value or the result of another promise,
     * and a reject callback used to reject the promise with a provided reason or error.
     */
    new <T>(executor: (resolve: (value: T | PromiseLike<T>) => void, reject: (reason?: any) => void) => void): Promise<T>;

    /**
     * Creates a Promise that is resolved with an array of results when all of the provided Promises
     * resolve, or rejected when any Promise is rejected.
     * @param values An array of Promises.
     * @returns A new Promise.
     */
    all<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10>(values: readonly [T1 | PromiseLike<T1>, T2 | PromiseLike<T2>, T3 | PromiseLike<T3>, T4 | PromiseLike<T4>, T5 | PromiseLike<T5>, T6 | PromiseLike<T6>, T7 | PromiseLike<T7>, T8 | PromiseLike<T8>, T9 | PromiseLike<T9>, T10 | PromiseLike<T10>]): Promise<[T1, T2, T3, T4, T5, T6, T7, T8, T9, T10]>;

    /**
     * Creates a Promise that is resolved with an array of results when all of the provided Promises
     * resolve, or rejected when any Promise is rejected.
     * @param values An array of Promises.
     * @returns A new Promise.
     */
    all<T1, T2, T3, T4, T5, T6, T7, T8, T9>(values: readonly [T1 | PromiseLike<T1>, T2 | PromiseLike<T2>, T3 | PromiseLike<T3>, T4 | PromiseLike<T4>, T5 | PromiseLike<T5>, T6 | PromiseLike<T6>, T7 | PromiseLike<T7>, T8 | PromiseLike<T8>, T9 | PromiseLike<T9>]): Promise<[T1, T2, T3, T4, T5, T6, T7, T8, T9]>;

    /**
     * Creates a Promise that is resolved with an array of results when all of the provided Promises
     * resolve, or rejected when any Promise is rejected.
     * @param values An array of Promises.
     * @returns A new Promise.
     */
    all<T1, T2, T3, T4, T5, T6, T7, T8>(values: readonly [T1 | PromiseLike<T1>, T2 | PromiseLike<T2>, T3 | PromiseLike<T3>, T4 | PromiseLike<T4>, T5 | PromiseLike<T5>, T6 | PromiseLike<T6>, T7 | PromiseLike<T7>, T8 | PromiseLike<T8>]): Promise<[T1, T2, T3, T4, T5, T6, T7, T8]>;

    /**
     * Creates a Promise that is resolved with an array of results when all of the provided Promises
     * resolve, or rejected when any Promise is rejected.
     * @param values An array of Promises.
     * @returns A new Promise.
     */
    all<T1, T2, T3, T4, T5, T6, T7>(values: readonly [T1 | PromiseLike<T1>, T2 | PromiseLike<T2>, T3 | PromiseLike<T3>, T4 | PromiseLike<T4>, T5 | PromiseLike<T5>, T6 | PromiseLike<T6>, T7 | PromiseLike<T7>]): Promise<[T1, T2, T3, T4, T5, T6, T7]>;

    /**
     * Creates a Promise that is resolved with an array of results when all of the provided Promises
     * resolve, or rejected when any Promise is rejected.
     * @param values An array of Promises.
     * @returns A new Promise.
     */
    all<T1, T2, T3, T4, T5, T6>(values: readonly [T1 | PromiseLike<T1>, T2 | PromiseLike<T2>, T3 | PromiseLike<T3>, T4 | PromiseLike<T4>, T5 | PromiseLike<T5>, T6 | PromiseLike<T6>]): Promise<[T1, T2, T3, T4, T5, T6]>;

    /**
     * Creates a Promise that is resolved with an array of results when all of the provided Promises
     * resolve, or rejected when any Promise is rejected.
     * @param values An array of Promises.
     * @returns A new Promise.
     */
    all<T1, T2, T3, T4, T5>(values: readonly [T1 | PromiseLike<T1>, T2 | PromiseLike<T2>, T3 | PromiseLike<T3>, T4 | PromiseLike<T4>, T5 | PromiseLike<T5>]): Promise<[T1, T2, T3, T4, T5]>;

    /**
     * Creates a Promise that is resolved with an array of results when all of the provided Promises
     * resolve, or rejected when any Promise is rejected.
     * @param values An array of Promises.
     * @returns A new Promise.
     */
    all<T1, T2, T3, T4>(values: readonly [T1 | PromiseLike<T1>, T2 | PromiseLike<T2>, T3 | PromiseLike<T3>, T4 | PromiseLike<T4>]): Promise<[T1, T2, T3, T4]>;

    /**
     * Creates a Promise that is resolved with an array of results when all of the provided Promises
     * resolve, or rejected when any Promise is rejected.
     * @param values An array of Promises.
     * @returns A new Promise.
     */
    all<T1, T2, T3>(values: readonly [T1 | PromiseLike<T1>, T2 | PromiseLike<T2>, T3 | PromiseLike<T3>]): Promise<[T1, T2, T3]>;

    /**
     * Creates a Promise that is resolved with an array of results when all of the provided Promises
     * resolve, or rejected when any Promise is rejected.
     * @param values An array of Promises.
     * @returns A new Promise.
     */
    all<T1, T2>(values: readonly [T1 | PromiseLike<T1>, T2 | PromiseLike<T2>]): Promise<[T1, T2]>;

    /**
     * Creates a Promise that is resolved with an array of results when all of the provided Promises
     * resolve, or rejected when any Promise is rejected.
     * @param values An array of Promises.
     * @returns A new Promise.
     */
    all<T>(values: readonly (T | PromiseLike<T>)[]): Promise<T[]>;

    // see: lib.es2015.iterable.d.ts
    // all<T>(values: Iterable<T | PromiseLike<T>>): Promise<T[]>;

    /**
     * Creates a Promise that is resolved or rejected when any of the provided Promises are resolved
     * or rejected.
     * @param values An array of Promises.
     * @returns A new Promise.
     */
    race<T>(values: readonly T[]): Promise<T extends PromiseLike<infer U> ? U : T>;

    // see: lib.es2015.iterable.d.ts
    // race<T>(values: Iterable<T>): Promise<T extends PromiseLike<infer U> ? U : T>;

    /**
     * Creates a new rejected promise for the provided reason.
     * @param reason The reason the promise was rejected.
     * @returns A new rejected Promise.
     */
    reject<T = never>(reason?: any): Promise<T>;

    /**
     * Creates a new resolved promise.
     * @returns A resolved promise.
     */
    resolve(): Promise<void>;

    /**
     * Creates a new resolved promise for the provided value.
     * @param value A promise.
     * @returns A promise whose internal state matches the provided promise.
     */
    resolve<T>(value: T | PromiseLike<T>): Promise<T>;
}

declare var Promise: PromiseConstructor;

/Applications/Visual Studio Code.app/Contents/Resources/app/extensions/node_modules/typescript/lib/lib.es2015.promise.d.ts

"use strict";

/**
 *
 * @author xgqfrms
 * @license MIT
 * @copyright xgqfrms
 * @created 2022-01-01
 *
 * @description TypeScript & Promise
 * @augments
 * @example
 * @link https://stackoverflow.com/questions/41078809/typescript-promise-generic-type
 *
 */

export {};

const log = console.log;

// const Generator = (datas:Array<string> = [], debug:boolean = false) => {
//     let result = ``;
//     // do something...
//     return result;
// };

function test(arg: string): Promise {
    return new Promise((resolve, reject) => {
        if (arg === "a") {
            resolve(1);
        } else {
            reject("1");
        }
    });
}
// ❌ Generic type 'Promise<T>' requires 1 type argument(s)

function test2(arg: string): Promise<number> {
    return new Promise((resolve, reject) => {
        if (arg === "a") {
            resolve(1);
        } else {
            reject("1");
        }
    });
}
// interface Promise<T>
// var Promise: PromiseConstructor
// new <number>(executor: (resolve: (value: number | PromiseLike<number>) => void, reject: (reason?: any) => void) => void) => Promise<number>

function test3(arg: string): Promise<string> {
    return new Promise((resolve, reject) => {
        if (arg === "a") {
            resolve(1);
            // (parameter) resolve: (value: string | PromiseLike<string>) => void
        } else {
            reject("1");
            // (parameter) reject: (reason?: any) => void
        }
    });
}
// ❌ Argument of type 'number' is not assignable to parameter of type 'string | PromiseLike<string>'.ts(2345)


function test4(arg: string): Promise<string | number> {
    return new Promise((resolve, reject) => {
        if (arg === "a") {
            resolve(1);
            // (parameter) resolve: (value: string | number | PromiseLike<string | number>) => void
        } else {
            reject("1");
            // (parameter) reject: (reason?: any) => void
        }
    });
}

/*

The generic type of the Promise should correspond to the non-error return-type of the function. The error is implicitly of type any and is not specified in the Promise generic type.

Promise 的泛型类型应该对应于函数的非错误返回类型。该错误是任何类型的隐式错误，并且未在 Promise 泛型类型中指定。

*/

function test5(arg: string): Promise<T> {
    return new Promise((resolve, reject) => {
        if (arg === "a") {
            resolve(1);
        } else {
            reject("1");
        }
    });
}
// ❌ Cannot find name 'T'.ts(2304)


function test6(arg: string): Promise<number, string> {
    return new Promise((resolve, reject) => {
        if (arg === "a") {
            resolve(1);
        } else {
            reject("1");
        }
    });
}
// ❌ Generic type 'Promise<T>' requires 1 type argument(s).ts(2314)


function test7(arg: string){
    return new Promise<number>((resolve, reject) => {
        if (arg === "a") {
            resolve(1);
        } else {
            reject("1");
        }
    });
}
// (parameter) resolve: (value: number | PromiseLike<number>) => void
// (parameter) reject: (reason?: any) => void

可选的类型系统

"use strict";

/**
 *
 * @author xgqfrms
 * @license MIT
 * @copyright xgqfrms
 * @created 2022-01-
 *
 * @description
 * @augments
 * @example
 * @link
 *
 */

export {};

const log = console.log;


// 隐式类型 （js）
var foo = 123;
foo = '456';
// Type 'string' is not assignable to type 'number'.ts(2322)

var bar = '123';
bar = 456;
// Type 'number' is not assignable to type 'string'.ts(2322)


// 显式类型 (ts)
var num: number = 123;
num = '456';
// Type 'string' is not assignable to type 'number'.ts(2322)

var str: string = '123';
str = 456;
// Type 'number' is not assignable to type 'string'.ts(2322)

refs

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