iterable-chain

LINQ-style chaining methods for iterables with strict type-checking.

• Better Types

Methods have various overloads for better type inference.For example, filter has 3 overloads:

interface Chain<T> {
  // normal
  filter(cb: Predicate<T>) : Chain<T>;
  // manual limit result to sub type
  filter<U extends T>(cb: Predicate<T>): Chain<U>;
  // explicit type protection to sub type
  filter<U extends T>(cb: TypeProtection<T, U>): Chain<U>;
}

• Fluent Interface

Use "chain"s to make your code more elegant.

function uncapitalize<S extends string>(s: S): Uncapitalize<S> {
  // ...
}
const obj = { "gEt": 1, "PoSt": 2, "puT": 3 };

const uncapitalized = Object.fromEntries(
  Object.entries(obj)
    .map(p => [uncapitalize(p[0]), p[1]])
);

const elegant = obj
  .toPairs()
  .map(([key, value]) => [uncapitalize(key), value] as const)
  // key is "gEt" | "poSt" | "puT" now
  .toDictionary(p => p[0], p => p[1]);

Install

npm install @lovekicher/iterable-chain or

yarn add @lovekicher/iterable-chain or

pnpm install @lovekicher/iterable-chain

Quick Start

Add Helper Methods(Optional)

import "@lovekicher/iterable-chain/global";

This will add helper methods(and type definitions) to the prototype or constructor of some primitive types, such as Array.prototype.chain, Array.range, Object.prototype.toPairs, etc.

Do this action only ONCE at the top of your code entry point

Use Chain

1. Create chain

import { chain } from "@lovekicher/iterable-chain";

const numbers = [1, 2, 3, 4, 5];

// From helper methods
const chain1 = numbers.chain();

// Or directly
const chain2 = chain(numbers);

2. Add chain operations and collectors

const chain = [
    [2018, 99],
    [2019, 327],
    [2020, 404],
    [2021, 653],
    [2022, 202],
  ]
  .chain()
  .orderBy(x => x[1], true)
  .map(x => x[1])
  .filter(x => x % 2 == 0)
  .map(x => "0x" + x.toString(16));
// All callback functions have not been called

const result = chain.toArray();
// `toArray` is a collect method, now get ["0x194", "0xca"]

const dict = [
    { owner: "foo", count: 3 },
    { owner: "bar", count: 10 },
    { owner: "baz", count: 16 },
  ]
  .chain()
  .toDictionary(x => x.owner, x => x.count);
/* {
  "foo": 3,
  "bar": 10,
  "baz": 16
} */