Koconut : Kotlin Style Collection Lib For Node.Js

Table of Contents

• Installation
• Introduction
• Components
• Necessity
• Examples
• Deprecation Warning
• License

Installation

Using npm

npm install koconut --save

Using yarn

yarn add koconut

Using bower (Browser env)

bower install [email protected]:ApexCaptain/Koconut.git

Introduction

This is a node.js library for collection(a.k.a data structure). It's fully written in TypeScript, but also compatible with JavaScript application. It's 100% Apache-2.0 licensed.

Here is a short example on how to use it:

TypeScript

import { KoconutArray } from 'koconut';

const sampleProcess = async () => {
  const myArray = KoconutArray.of(1, 2, 3, 4, 5, 6);

  const evenNumbers = await myArray
    .filter((eachNumber) => eachNumber % 2 == 0)
    .yield();

  console.log(evenNumbers);
  // ↑ [ 2, 4, 6 ]
};
sampleProcess();

JavaScript (CommonJs)

const { KoconutArray } = require('koconut');

const sampleProcess = async () => {
  const myArray = KoconutArray.of(1, 2, 3, 4, 5, 6);

  const evenNumbers = await myArray
    .filter((eachNumber) => eachNumber % 2 == 0)
    .yield();

  console.log(evenNumbers);
  // ↑ [ 2, 4, 6 ]
};
sampleProcess();

As you can see, there's no big difference between using it in JS and TS. Both examples created a 1 to 6 integer array and filtered only the even numbers.

Components

Documents

The full document of this library is running on git-hub page.

Container

• KoconutEntry
• Entry
• KoconutPair
• Pair
• KoconutArray
• KoconutSet
• KoconutMap

Enum

• KoconutLocale
• KoconutLoopSignal

Exception

• KoconutConflictException
• KoconutIndexOutOfBoundsException
• KoconutInvalidArgumentException
• KoconutNoSuchElementException

Protocol (Interface)

• KoconutComparable
• KoconutEquatable

Tool

• KoconutOption

Hierarchy

This is the Koconut class hierarchy in current version.

Necessity

OK, so... why do I need it?

Koconut is promise-friendly. The basic design philsophy of this library is to use async/await functionality without any interruption even if whlie using iterative process. Let me give you an example.

Imagine if there are 3 different http requests info. Each and every one of them has a very different purpose and cannot be merged into a single requset. You may want to handle them one by one sequentially.

const requestInfoList = [
  {
    method: 'POST',
    uri: 'https://myServer',
    data: {
      some: 'payload1',
    },
  },
  {
    method: 'GET',
    uri: 'https://myServer',
    data: {
      some: 'payload2',
    },
  },
  {
    method: 'DELETE',
    uri: 'https://myServer',
    data: {
      some: 'payload3',
    },
  },
];

Now, let's send those requests with one of the most common http node.js lib, axios.

const mainProcess = async () => {
  const results = new Array();
  requestInfoList.forEach(async (eachRequestInfo) => {
    const eachResult = await axios(eachRequestInfo);
    results.push(eachResult);
  });

  console.log(results); // --- [1] : Empty List
  console.log('Nailed it!');
};
mainProcess();

Within upper example, each http request is handled asynchronously. However, the result of outer forEach function of normal Array is not a Promise instance, in other words, it does not support Promise nor async/await.

Therefore, printed message at [1] is gonna be an empty list. This is definitely not what you've intended.

Now, you have to come up with a different way. Maybe, after some Googling and Googling (Like as I did), you'll find an answer just like below.

const mainProcess = async () => {
  const results = new Array();
  for (const eachRequestInfo of requestInfoList) {
    const eachResult = await axios(eachRequestInfo);
    results.push(eachResult);
  }

  console.log(results); // --- [1] : [ result1, result2, result3 ]
  console.log('Nailed it!');
};
mainProcess();

By doing this, all the requests are sent one by one. Printed message at [1] would be an array of three request results.

The problem is resolved! Having a nice cuppa tea, reclining your seat, wow, you may leave work early today!

Or... is it?

The next day, your boss told you that each request result should be checked whether it's valid or not.

The information you need is all in some other database. So, you made another async function called checkIsValid.

Easy! It can be done like this.

const mainProcess = async () => {
  const results = new Array();
  for (const eachRequestInfo of requestInfoList) {
    const eachResult = await axios(eachRequesInfo);
    results.push(eachResult);
  }

  const validResults = new Array();
  for (const eachResult of results) {
    if (await checkIsValid(eachResult)) validResults.push(eachResult);
  }

  console.log(validResults); // --- [1] : Valid results matches the given condition
  console.log('Nailed it!');
};
mainProcess();

Now you have two different arrays. This is the problem. Since previous iterable classes don't support Promise, you have to keep adding for...of or for...in statement over and over again into your source code. As time goes by and your software becomes more and more complicated, your data processing would be messy and unrecognizable.

It would be great just if you can use filter function instead, right?

Well, here's an example using KoconutArray.

import { KoconutArray } from 'koconut';
const mainProcess = async () => {
  const validResults = await KoconutArray.from(requestInfoList)
    .map(axios)
    .filter(checkIsValid)
    .yield();

  console.log(validresults);
  console.log('Nailed it!');
};
mainProcess();

Boom! It is done! No more complicated for...of or for...in iterative processes. It is safe and quite beautiful. Of course, I know that it's pretty unnatural example. You could fetch result and validate it simultaneously just in one loop. But by drawing upon Koconut library, your source code would be much more clear and efficient.

Examples

Let me give you a few examples for basic usage of this library. I've written only about KoconutArray as a representative class.

Creation

To create a KoconutArray instance, you can do it in 4 different ways.

1. Using new keyword.

   Very traditional way. You can create a new instance from an iterable object or if it's ommitted you may have an empty array. In case of that, you'd better declare generic type explicitly.

   import { KoconutArray } from 'koconut';
   
   const emptyKoconutNumbers = new KoconutArray<number>();
   // ↑ This is an empty Koconut number array
   
   const numbers = Array.of(1, 2, 3, 4, 5);
   const koconuntNumbers = new KoconutArray(numbers);
   // ↑ This is a Koconut number array consists of 1 to 5.

2. Using static from method.

   You can create a new instance from an iterable object.

   import { KoconutArray } from 'koconut';
   
   const numbers = Array.of(1, 2, 3, 4, 5);
   const koconutNumbers = KoconutArray.from(numbers);
   // ↑ This is a Koconut number array consists of 1 to 5.

3. Using static of method.

   You can create a new instance with a variable number of arguments

   import { KoconutArray } from 'koconut';
   
   const koconutNumbers = KoconutArray.of(1, 2, 3, 4, 5);
   // ↑ This is a Koconut number array consists of 1 to 5.

4. Using static generate method.

   This method creates a new instance with length positions and fills it with values provided by generator function callback with each index in the range "0...length - 1" in increasing order as an argument. Given count must be non-negative number.

   import { KoconutArray } from 'koconut';
   
   const evenNumberArray = await KoconutArray.generate(5, (i) => i * 2);
   // ↑ This is a Koconut number array consists of 2, 4, 6, 8 and 10.
   
   const negativeLength = await KoconutArray.generate(-1, (i) => i * 2);
   // ↑ This will cause invalid argument exception since given count is a negative number.

Processing

All the Koconut containers internally connected with each other within Promise chain. In a nutshell, you have to process all the chained objects before you get the result. There are 3 ways to do that. They're almost same but slightly different.

1. Using yield method.

   This method processes all the chained objects and returns the result.

   import { KoconutArray } from 'koconut';
   
   const mainProcess = async () => {
     const koconutNumbers = KoconutArray.of(1, 2, 3, 4, 5);
   
     const firstNumber = await koconutNumbers.first().yield();
     console.log(firstNumber);
     // ↑ 1
   };
   mainProcess();

2. Using process method.

   This method just simply processes all the chained objects, then return Promise<void>.

   import { KoconutArray } from 'koconut';
   
   const mainProcess = async () => {
     const koconutNumbers = KoconutArray.of(1, 2, 3, 4, 5);
   
     await koconutNumbers.forEach(console.log).process();
     // ↑ 1 2 3 4 5
   };
   mainProcess();

3. Using let method.

   This method processes all the chained objects and calls the specified function block with the reuslt value as its argument and returns the final result of the block.

   import { KoconutArray } from 'koconut';
   
   const mainProcess = async () => {
     const koconutNumbers = KoconutArray.of(1, 2, 3, 4, 5);
   
     const firstNumberPlus2 = await koconutNumbers
       .first()
       .let((result) => result + 2);
     console.log(firstNumber);
     // ↑ 3
   };
   mainProcess();

4. Using also method.

   This method processes all the chained objects and calls the specified function block with the result value as its argument and return passed result object.

   import { KoconutArray } from 'koconut';
   
   const mainProcess = async () => {
     const koconutNumbers = KoconutArray.of(1, 2, 3, 4, 5);
   
     const moreNumbers = await koconutNumbers.also((result) => {
       result.push(6);
       result.push(7);
       result.push(8);
     });
     console.log(moreNumbers);
     // ↑ [1, 2, 3, 4, 5, 6, 7, 8]
   };
   mainProcess();

Iteration

Iterative methods of KoconutArray are forEach, forEachIndexed, onEach and onEachIndexed. These methods loop to repeat given action.

Methods of which names start with for return nothing.

Methods start with on return the original collection itself.

import { KoconutArray } from 'koconut';

const mainProcess = async () => {
  const koconutNumbers = KoconutArray.of(1, 2, 3, 4, 5);

  const resultOfForEach = await koconutNumbers
    .forEach(console.log)
    // ↑ 1 2 3 4 5
    .yield();
  console.log(resultOfForEach);
  // ↑ undefined

  const resultOfOnEach = await koconutNumbers
    .onEach(console.log)
    // ↑ 1 2 3 4 5
    .yield();
  console.log(resultOfForEach);
  // ↑ [1, 2, 3, 4, 5]
};
mainProcess();

And of course, methods of which name end with indexed have action block given with two arguments.

One is index, and the other is element.

If you want to interrupt, in other word stop the iteration process in the meantime, you may return false or KoconutLoopSignal.BREAK.

Calculation

Each calculator method has its own purpose, performing calculation according to the established rules. For instance, maxBy method returns the first element yielding the largest value of the given function block.

import { KoconutArray } from 'koconut';

const mainProcess = async () => {
  const koconutArray = KoconutArray.of(1, 2, 3, 4, 5);

  const largestNumberOfArray = await koconutArray
    .maxBy((eachNumber) => eachNumber)
    .yield();
  console.log(largestNumberOfArray);
  // ↑ 5

  try {
    await koconutArray
      .filter((eachNumber) => eachNumber > 10)
      .maxBy((eachNumber) => eachNumber)
      .yield();
  } catch (error) {
    console.log(error.name);
    // ↑ Koconut No Such Element Exception
    // i.e. -- Array is filtered.
    // No element in 1 to 5 is greater than 10.
  }
};
mainProcess();

Manipulation

Manipulator methods rearrange the collection, add new elements or filter it by given condition. For instance, sortedBy method returns a collection of all elements sorted according to natural sort order(ASC) of the value returned by specified selector function block.

import { KoconutArray } from 'koconut';

const mainProcess = async () => {
  const koconutArray = KoconutArray.of('abcd', 'ab', 'abc', 'a');

  const sortedStringArrayByLength = await koconutArray
    .sortedBy((eachString) => eachString.length)
    .yield();
  console.log(sortedStringArrayByLength);
  // ↑ [ 'a', 'ab', 'abc', 'abcd' ]
};
mainProcess();

Inspection

Inspector methods check the elements at given condtion. For instance, all method return true if all elements match the given predicate function block. If any one of those elements doesn't meet the condtion, it'll return false.

import { KoconutArray } from 'koconut';

const mainProcess = async () => {
  const koconutArray = KoconutArray.of(1, 2, 3, 4, 5);

  const areAllArrayElementsGreaterThan0 = await koconutArray
    .all((eachNumber) => eachNumber > 0)
    .yield();
  console.log(areAllArrayElementsGreaterThan0);
  // ↑ true

  const areAllArrayElementsEven = await koconutArray
    .all((eachNumber) => eachNumber % 2 == 0)
    .yield();
  console.log(areAllArrayElementsEven);
  // ↑ false -- i.e. '1' is not an even number.
};
mainProcess();

Transformation

Transformer methods convert the collection into other format. The map method is representative. It returns a list containing the results of applying the given transform function block to each element in the original collection.

import { KoconutArray } from 'koconut';

const mainProcess = async () => {
  const koconutArray = KoconutArray.of(1, 2, 3, 4, 5);

  const dobuledNumbers = await koconutArray
    .map((eachNumber) => eachNumber * 2)
    .yield();
  console.log(dobuledNumbers);
  // ↑ [ 2, 4, 6, 8, 10 ]

  const numberStrings = await koconutArray
    .map((eachNumber) => eachNumber.toString())
    .yield();
  console.log(numberStrings);
  // ↑ [ '1', '2', '3', '4', '5' ]
};
mainProcess();

Deprecation Warning

Introduction

Some methods might no longer be supported in the future. If you have used any one of them, your application is gonna be crashed after updating the library with no reason. To prevent such troubles, Koconut supports Deprecation Warning functionality since version 1.0.10.

What does that mean?

Example

For instance, maxBy method in KoconutArray returns the first element yielding the largest value of the given function or throw KoconutNoSuchElementException when there is no element. Following examples are same as written in document page.

import { KoconutArray } from 'koconut';

const main = async () => {
  // Create an 1 to 5 number array.
  const koconutArray = KoconutArray.of(1, 2, 3, 4, 5);

  // 1st example. Finding largest number.
  const largestNumberOfArray = await koconutArray
    .maxBy((eachNumber) => eachNumber)
    .yield();
  console.log(largestNumberOfArray);
  // ↑ 5

  // 2nd example. Finding largest number of an empty array.
  try {
    await koconutArray
      .filter((eachNumber) => eachNumber > 10) // <-- Now, it's empty
      .maxBy((eachNumber) => eachNumber) // <-- This is impossible
      .yield();
  } catch (error) {
    console.log(error.name);
    // ↑ Koconut No Such Element Exception
    // i.e. -- Array is filtered.
    // No element in 1 to 5 is greater than 10.
  }
};
main();

The first example returns 5, which is of course, the largest value of the array.

However in the second one, maxBy method throws an error because you've just tried to get an element in an empty array. If this error had not been caught, the whole application would be termintaed.

This is why maxBy method is depreacted, and also why usage of maxByOrNull method is recommended. It'll just return null if the array is empty.

The problem is that you might not have known about it. You must be warned before that happens and that's where the Deprecation Warning comes in. When you use a method that is gonna be depreacted someday, Koconut will notice you that "Oh, this method is not supported any more. You'd better use this one instead.".

Language Support

Currently, Deprecation Warning of Koconut supports three languages.

Locale setting is done automatically. If you are in Japan, message will be printed in Japanese. If you are in Korea it'll be Korean or if you're in States, English will be your default locale.

If you want more detail, please have a check here.

Options

There are three options you can change for Depreation Warning.

• Locale

  You can chagne the language explicitly. Default value depends on your actual region. If it's not supported, en(English) will be the default. For instance, if you're in China or Russia, default locale is just English. I'm sorry I cannot handle them all...

  import { KoconutOption, KoconutLocale } from 'koconut';
  
  KoconutOption.locale = KoconutLocale.en; // English
  KoconutOption.locale = KoconutLocale.ja; // Japanese
  KoconutOption.locale = KoconutLocale.ko; // Korean

• Availability

  Simply, if you don't want to use Depreaction Warning set the flag to false. Default value is true.

  import { KoconutOption } from 'koconut';
  
  KoconutOption.isDeprecationWarningEnabled = true; // Enabled (Default)
  KoconutOption.isDeprecationWarningEnabled = false; // Disabled

• Call Stack

  If you don't want to see messy call stack of the warning, you just disable it by setting the flag to false.

  import { KoconutOption } from 'koconut';
  
  KoconutOption.doesDeprecationWarningShowCallStack = true; // Enabled (Default)
  KoconutOption.doesDeprecationWarningShowCallStack = false; // Disabled

License

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

   http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.