Object pool with a private pool array

object-pool-no-linked-list.js

const INCREASE_PERCENT = 50;
const MINIMUM_PERCENT_FREE = 10;
const NULL_ELEMENT = null;

class ObjectPool {
  #poolArray = [];
  #freeElements = 0;
  #freeIndex = 0;

  resetFunction = () => {
  };
  constructorFunction = () => {
  };


  constructor(constructorFunction, resetFunction = obj => obj, initialSize = 1000) {
    this.resetFunction = resetFunction;
    this.constructorFunction = constructorFunction;
    for (let i = 0; i < initialSize; i++) this.createElement();
  }

  createElement() {
    this.#freeElements++;
    this.#poolArray.push(this.resetFunction(this.constructorFunction()));
    return this.#poolArray[this.#poolArray.length - 1];
  }

  increasePoolSize() {
    const increaseSize = Math.round(INCREASE_PERCENT * this.#poolArray.length / 100);
    for (let i = 0; i < increaseSize; i++) {
      this.createElement();
    }
    this.#freeElements += increaseSize;
  }

  getElement() {
    if (this.#freeElements / this.#poolArray.length <= MINIMUM_PERCENT_FREE / 100) {
      this.increasePoolSize();
    }
    this.#freeElements--;
    const freeElement = this.#poolArray[this.#freeIndex];
    this.#poolArray[this.#freeIndex++] = NULL_ELEMENT;
    return freeElement;
  }

  releaseElement(element) {
    this.#poolArray[--this.#freeIndex] = element;
    this.resetFunction(element);
  }

  get size() {
    return this.#poolArray.length;
  }
}

object-pool.js

const INCREASE_PERCENT = 50;
const MINIMUM_PERCENT_FREE = 10;

class ObjectPoolMember {
  previousElement = null;
  nextElement = null;
  free = true;

  constructor(data) {
    this.data = data;
  }
}

class ObjectPool {
  #poolArray = [];
  #freeElements = 0;
  #nextFree = null;
  #lastFree = null;

  resetFunction = () => {
  };
  constructorFunction = () => {
  };


  constructor(constructorFunction, resetFunction = obj => obj, initialSize = 1000) {
    this.resetFunction = resetFunction;
    this.constructorFunction = constructorFunction;
    for (let i = 0; i < initialSize; i++) this.createElement();
    this.#nextFree = this.#poolArray[0];
  }

  createElement() {
    this.#freeElements++;
    const data = this.resetFunction(this.constructorFunction());
    const newObjectPoolMember = new ObjectPoolMember(data);
    this.#poolArray.push(newObjectPoolMember);

    if (!this.#lastFree) {
      this.#lastFree = newObjectPoolMember;
    } else {
      this.linkElement(newObjectPoolMember);
    }

    return newObjectPoolMember;
  }

  linkElement(element) {
    element.previousElement = this.#lastFree;
    this.#lastFree.nextElement = element;
    this.#lastFree = element;
  }

  unlinkFirstElement(element) {
    this.#nextFree = element.nextElement;
    this.#nextFree.previousElement = null;
    element.nextElement = this.previousElement = null;
  }

  catchElement(element) {
    element.free = false;
    this.#freeElements--;
    if (this.#freeElements / this.#poolArray.length < MINIMUM_PERCENT_FREE / 100) {
      const increaseSize = Math.round(INCREASE_PERCENT * this.#poolArray.length / 100);
      for (let i = 0; i < increaseSize; i++) {
        this.createElement();
      }
      this.#freeElement += increaseSize;
    }
  }

  getElement() {
    const availableElement = this.#nextFree;
    this.unlinkFirstElement(availableElement);
    this.catchElement(availableElement);
    return availableElement;
  }

  setElementAsFree(element) {
    element.free = true;
    this.linkElement(element);
    this.#freeElements++;
  }

  releaseElement(element) {
    this.setElementAsFree(element);
    this.resetFunction(element.data);
  }
}