Class Stack

17-iterators-data-structures/08-stacks/script.js:1–48

class Stack {
  constructor() {
    this._items = [];
    this._count = 0;
  }

  push(item) {
    this._items[this._count] = item;
    this._count++;
  }

  pop() {
    if (this.isEmpty()) {
      return 'Underflow';
    }

    const item = this._items[this._count - 1];
    this._count--;

    for (let i = this._count; i < this._items.length; i++) {
      this._items[i] = this._items[i + 1];
    }

    this._items.length = this._count;
    return item;
  }

  peek() {
    if (this.isEmpty()) {
      return 'No items in stack';
    }

    return this._items[this._count - 1];
  }

  isEmpty() {
    return this._count === 0;
  }

  length() {
    return this._count;
  }

  clear() {
    this._items = [];
    this._count = 0;
  }
}

const stack = new Stack();