Class Stack

chapter03/util/Stack.js:12–41

- size()
*/
class Stack {
  constructor() {
    this._data = [];
  }

  size() {
    return this._data.length;
  }

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

  push(value) {
    this._data.push(value);
  }

  pop() {
    return this._data.pop();
  }

  peek() {
    if (this.isEmpty()) return null;
    return this._data[this.size() - 1];
  }

  _toArray() {
    return this._data;
  }
}

module.exports = Stack;