tutorials-files/stack2.js at master · beforesemicolon/tutorials-files · GitHub

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class Stack {
  #lastItem = null;
  #size = 0;
  #capacity = null;

  constructor(capacity = null) {
    this.#capacity = Math.max(Number(capacity), 0) || null;
  }

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

  get isEmpty() {
    return this.size === 0;
  }

  get isFull() {
    return this.#capacity ? this.size === this.#capacity : false;
  }

  #createItem(value) {
    return {
      prev: null,
      value
    }
  }

  push(item) {
    if(!this.isFull) {
      const newItem = this.#createItem(item);

      if(!this.isEmpty) {
        newItem.prev = this.#lastItem;
      }

      this.#lastItem = newItem;
      this.#size += 1;
    }

    return this.size;
  }

  pop() {
    let removedItem = null;

    if(!this.isEmpty) {
      removedItem = this.#lastItem.value;
      this.#lastItem = this.#lastItem.prev;
      this.#size -= 1;
    }

    return removedItem;
  }

  peek() {
    return this.#lastItem.value;
  }

  toString() {
    if(this.isEmpty) {
      return '';
    }

    let current = this.#lastItem;
    let str = `${current.value}`;

    while(current.prev) {
      current = current.prev;
      str = `${current.value},${str}`;
    }

    return str;
  }
}