如何使用 "p-waterfall" TypeScript 类型

How to use "p-waterfall" TypeScript Types

我正在使用 p-waterfall and I would like to know how to use the TypeScript types provided. Here are the types

declare namespace pWaterfall {
  type Task<ValueType, ReturnType> = (
    previousValue: ValueType
  ) => ReturnType | PromiseLike<ReturnType>;

  type InitialTask<ReturnType> = () => ReturnType | PromiseLike<ReturnType>;
}

declare const pWaterfall: {
    <ReturnType>(tasks: [pWaterfall.InitialTask<ReturnType>]): Promise<ReturnType>;
  <ValueType1, ReturnType>(
    tasks: [
      pWaterfall.InitialTask<ValueType1>,
      pWaterfall.Task<ValueType1, ReturnType>
    ]
  ): Promise<ReturnType>;
  <ValueType1, ValueType2, ReturnType>(
    tasks: [
      pWaterfall.InitialTask<ValueType1>,
      pWaterfall.Task<ValueType1, ValueType2>,
      pWaterfall.Task<ValueType2, ReturnType>
    ]
  ): Promise<ReturnType>;
  ...

我放了一个example (code below) together that if typed would really help me understand how to get the types working with p-waterfall.

import pWaterfall from "p-waterfall";

interface User {
  name: string;
}

const getItemsRequest = async (sliceCount: number): Promise<User[]> => {
  return [{ name: "a" }, { name: "b" }, { name: "c" }].slice(0, sliceCount);
};

const getNames = (results: User[]): string[] => {
  return results.map(item => item.name);
};

const countArrayLength = <T extends unknown[]>(results: T): number => {
  return results.length;
};

(async () => {
  const transformers = [getItemsRequest, getNames, countArrayLength];

  const shouldBeTypeNumberButIsUnknown = await pWaterfall(transformers, 2);

  console.log(`results`, shouldBeTypeNumberButIsUnknown); // 2
})();

shouldBeTypeNumberButIsUnknown 未知但应该是 number 因为最后一个函数传入 pWaterfall returns 一个数字。

我已经为 p-waterfall 打开了一个 PR,它可以让你轻松地做你想做的事。 See here.

同时,您可以使用两种解决方法:

  1. 你可以直接用我的fork:

    • npm uninstall p-waterfall
    • npm install https://github.com/sindresorhus/p-waterfall/tarball/c6802cc6c55f00803a3262db2f119c69d07241ec
    • 然后使用我在 GitHub 问题
    • 中解释的 const 断言
  2. 可以直接传递transformers数组,不需要创建中间变量。这样 p-waterfall 就会正确处理。 See on StackBlitz