JSPM

import { fluent, FluentIterable } from 'fluent-iterable';

const numbers: number[] = [3, 1, 8, 6, 9, 2];
const iterable: FluentIterable<number> = fluent(numbers);

console.log(
  `The largest even number is: ${iterable.filter((n) => n % 2 === 0).max()}`,
);

import fetch from 'node-fetch';
import {
  fluent,
  fluentAsync,
  FluentIterable,
  FluentAsyncIterable,
} from 'fluent-iterable';

const iterableOfArray: FluentIterable<number> = fluent([3, 1, 8, 6, 9, 2]);

function* naiveFibonacci(): Iterable<number> {
  yield 0;
  yield 1;

  let x = 0;
  let y = 1;

  while (true) {
    y = x + y;
    x = y - x;
    yield y;
  }
}

const iterableOfGenerator: FluentIterable<number> = fluent(naiveFibonacci());

async function* emails(): AsyncIterable<string> {
  let page = 1;
  while (true) {
    const res = await fetch(`https://reqres.in/api/users?page=${page}`);
    if (!res.ok) {
      break;
    }
    yield* (await res.json()).data.map((user) => user.email);
  }
}

const asyncIterableOfEmails: FluentAsyncIterable<string> = fluentAsync(
  emails(),
);

...

interface ChatMessage {
  id: number;
  from: string;
  to: string;
  body: string;
}

...

function getAllMessages(iterable: FluentAsyncIterable<ChatMessage>): FluentAsyncIterable<string> {
  return iterable.map(chatMessage => chatMessage.body);
}

function getAllUsers(iterable: FluentAsyncIterable<ChatMessage>): FluentAsyncIterable<string> {
  return iterable
    .flatten(chatMessage => [ chatMessage.from, chatMessage.to ]) // convert the message entries into arrays of sender and recipient and flatten them
    .distinct(); // yield the users only once
}

function getNumberOfUsers(iterable: FluentAsyncIterable<ChatMessage>): Promise<number> {
  return getAllUsers(iterable).count();
}

async function getMostActiveUser(iterable: FluentAsyncIterable<ChatMessage>): Promise<string> {
  const maxGroup: FluentGroup<ChatMessage> = await iterable
    .group(chatMessage => chatMessage.from) // group the messages by their sender
    .max(chatMessage => chatMessage.values.count()); // find one of the groups which has the most messages
  return maxGroup.key;
}

async function hasUserSentEmptyMessage(iterable: FluentAsyncIterable<ChatMessage>, user: string): Promise<bool> {
  return await iterable
    .any(chatMessage => chatMessage.from === user && chatMessage.body.length === 0); // will stop reading elements as soon as found one which satisfying the condition
}

async function createBackupSequential(iterable: FluentAsyncIterable<ChatMessage>): Promise<void> {
  await iterable
    .execute(chatMessage => console.log(`Backing up message ${chatMessage.id}.`)) // log progress w/o modifying the iterable
    .forEachAsync(chatMessage => fetch(BACKUP_URL, { // execute the asynchronous backup operation against all elements one-by-one
      method: 'post',
      body:    JSON.stringify(chatMessage),
      headers: { 'Content-Type': 'application/json' },
    }));
}

async function createBackupParallel(iterable: FluentAsyncIterable<ChatMessage>): Promise<void> {
  const promises = iterable
    .execute(chatMessage => console.log(`Backing up message ${chatMessage.id}.`)) // log progress w/o modifying the iterable
    .map(chatMessage => fetch(BACKUP_URL, { // translate all elements into a promise of their asynchronous backup operation
      method: 'post',
      body:    JSON.stringify(chatMessage),
      headers: { 'Content-Type': 'application/json' },
    }));
  await Promise.all(promises);
}

import { fluent, interval } from 'fluent-iterable';

const numbers: Iterable<number> = interval();
const iterable: FluentIterable<number> = fluent(numbers);

for (const number of iterable.take(10)) {
  // generate the first 10 numbers one-by-one
  console.log(number);
} // close the generator

// this function would cause an infinite loop:
// for (const number of iterable.take(10)) { // generate infinite number of numbers one-by-one
//   console.log(number);
// }

import { fluentAsync, depaginate, Page, Pager } from 'fluent-iterable';

interface Data { .. } // The type of the data stored in the paginated resource
type NextPageToken = ..; // The type of the next page token (e.g. page number, DDB token string, etc)

// These functions return a page of items from the resource in the form of { nextPageToken: NextPageToken, results: Data[] }
async function getFirstPage(): Promise<Page<Data, NextPageToken>> { .. }
async function getPage(nextPageToken: NextPageToken): Promise<Page<Data, NextPageToken>> { .. }

const pager: Pager<Data, NextPageToken> = (nextPageToken) => nextPageToken ? getPage(nextPageToken) : getFirstPage();

const allItems: AsyncIterable<Data> = depaginate(pager); // as long as you keep read items from this it will keep requesting pages to fulfil the reads
const firstItems: FluentAsyncIterable<Data> = fluentAsync(depaginate(pager)).take(10); // you can read up to 10 items from this and it will request exactly as many pages as necessary to fulfill the reads

// ... you get the picture

import { fluent } from 'fluent-iterable';

function* naiveFibonacci(): Iterable<number> {
  yield 0;
  yield 1;

  let x = 0;
  let y = 1;

  while (true) {
    y = x + y;
    x = y - x;
    yield y;
  }
}

// What is the sum of the first 100 fibonacci numbers?
console.log(
  fluent(naiveFibonacci())
    .takeWhile((n) => n < 100)
    .sum(),
);

// How many fibonacci numbers are there between 1K and 1M?
console.log(
  fluent(naiveFibonacci())
    .skipWhile((n) => n < 1000)
    .takeWhile((n) => n < 1000000)
    .count(),
);

// What are the 10th to 20th fibonacci numbers?
console.log(fluent(naiveFibonacci()).skip(9).take(10).toArray());

// What are the halves of the first 20 even fibonacci numbers?
console.log(
  fluent(naiveFibonacci())
    .filter((n) => n % 2 === 0)
    .take(20)
    .map((n) => n / 2)
    .toArray(),
);

import { fluent } from 'fluent-iterable';

enum Gender {
  Male = 'Male',
  Female = 'Female',
  NonBinary = 'NonBinary',
}

interface Person {
  name: string;
  gender?: Gender;
  emails: string[];
}

const people: Person[] = [
  {
    name: 'Adam',
    gender: Gender.Male,
    emails: ['adam@adam.com'],
  },
  {
    name: 'Christine',
    gender: Gender.Female,
    emails: [],
  },
  {
    name: 'Sebastian',
    emails: ['sebastian@sebastian.com', 'sebastian@corp.com'],
  },
  {
    name: 'Alex',
    gender: Gender.Female,
    emails: ['alex@alex.com'],
  },
];

// Log all the names!
for (const name of fluent(people).map((p) => p.name)) {
  console.log(name);
}

// Log all the emails!
console.log(
  fluent(people)
    .flatten((p) => p.emails)
    .toArray(),
);

// Are there any persons without gender specified?
console.log(fluent(people).any((p) => !p.gender));

// Are all the persons have at least one email?
console.log(fluent(people).all((p) => p.emails.length > 0));

// Who is the last female?
console.log(fluent(people).last((p) => p.gender === Gender.Female));

// Who is the last one in lexicographical order?
console.log(
  fluent(people)
    .sort((a, b) => a.name.localeCompare(b.name))
    .last(),
);

// Log all persons grouped by gender!
console.log(
  fluent(people)
    .group((p) => p.gender)
    .map(
      (grp) =>
        `${fluent(grp.values)
          .map((p) => p.name)
          .toArray()
          .join(', ')} is/are ${grp.key}`,
    )
    .reduce((current, next) => `${current}\n${next}`, ''),
);

import fetch from 'node-fetch';
import { fluentAsync, Pager } from 'fluent-iterable';

interface Data {
  id: number;
  email: string;
  avatar: string;
}

const pager: Pager<Data, number> = async (token?: number) => {
  const page = token || 1;
  const res = await fetch(`https://reqres.in/api/users?page=${page}`);
  return {
    results: res.ok ? (await res.json()).data : undefined,
    nextPageToken: page + 1,
  };
};

// Get the first 10 emails sorted!
fluentAsync(depaginate(pager))
  .map((data) => data.email)
  .take(10)
  .sort()
  .forEach((res) => console.log(res))
  .then(() => console.log('done'));

import { fluent, identity } from 'fluent-iterable';

const genders = [
  { code: 'm', description: 'male' },
  { code: 'f', description: 'female' },
  { code: 'n', description: 'non binary' },
];

const persons = [
  {
    name: 'Steve',
    gender: 'm',
  },
  {
    name: 'Natasha',
    gender: 'f',
  },
  {
    name: 'Lucius',
    gender: 'n',
  },
  {
    name: 'Jonathan',
    gender: 'm',
  },
  {
    name: 'Nicole',
    gender: 'f',
  },
  {
    name: 'Emmy',
    gender: 'n',
  },
];

fluent(genders)
  .combine(
    persons,
    (g) => g.code,
    (p) => p.gender,
  )
  .forEach(([gender, person]) =>
    console.log(`name: ${person.name}, gender: ${gender.description}`),
  );

import { DynamoDB } from 'aws-sdk';
import { Key } from 'aws-sdk/clients/dynamodb';
import { depaginate, fluentAsync, Pager } from 'fluent-iterable';

async function *scan<TData>(
  input: DynamoDB.DocumentClient.ScanInput
): AsyncIterable<TData> {
  const ddb = new DynamoDB.DocumentClient(..);
  const pager: Pager<TData, Key> = async (token) => {
    const result = await ddb
      .scan(input)
      .promise();

    return {
      nextPageToken: result.LastEvaluatedKey,
      results: result.Items as TData[],
    };
  };

  yield* depaginate(pager);
}

// and use it like this:

const productsParams: DynamoDB.DocumentClient.ScanInput = {
  TableName : 'ProductTable',
  FilterExpression : '#shoename = :shoename', // optional
  ExpressionAttributeValues : {':shoename' : 'yeezys'}, // optional
  ExpressionAttributeNames: { '#shoename': 'name' } // optional
};

async function printProducts(count: number) {
  for await (const product of fluentAsync(scan(productsParams)).take(count)) {
    console.dir(product);
  }
}

declare module '@codibre/fluent-iterable' {
  import { extendAsync } from '../src';

  interface FluentAsyncIterable<T> {
    myCustomIterableMethod(): FluentAsyncIterable<T>;
    myCustomResolvingMethod(): PromiseLike<number>;
  }

  extendAsync.use('myCustomIterableMethod', (x) => someOperation(x));
  extendAsync.use('myCustomResolvingMethod', (x) => someResolvingOperation(x));
}