javascript - 力扣 代码执行为什么会出错呢？

Question

var NestedIterator = function (nestedList) {
  function loop(arr, data) {
    if (Array.isArray(arr))
      arr.forEach((e) => {
        if (Array.isArray(e)) loop(e, data);
        else data.push(e);
      });
    else data.push(arr);
  }
  this.index = 0;
  this.Array = []; 
  loop(nestedList, this.Array);
}; 
NestedIterator.prototype.hasNext = function () {
  return this.index < this.Array.length  ;
}; 
NestedIterator.prototype.next = function () {
  if (this.index < this.Array.length  ) return this.Array[this.index++];
  return null;
};

题目地址 ： https://leetcode.cn/problems/flatten-nested-list-iterator/
为什么会出错呢？

Answer 1

/**
 * // This is the interface that allows for creating nested lists.
 * // You should not implement it, or speculate about its implementation
 * function NestedInteger() {
 *
 *     Return true if this NestedInteger holds a single integer, rather than a nested list.
 *     @return {boolean}
 *     this.isInteger = function() {
 *         ...
 *     };
 *
 *     Return the single integer that this NestedInteger holds, if it holds a single integer
 *     Return null if this NestedInteger holds a nested list
 *     @return {integer}
 *     this.getInteger = function() {
 *         ...
 *     };
 *
 *     Return the nested list that this NestedInteger holds, if it holds a nested list
 *     Return null if this NestedInteger holds a single integer
 *     @return {NestedInteger[]}
 *     this.getList = function() {
 *         ...
 *     };
 * };
 */

/**
 * @constructor
 * @param {NestedInteger[]} nestedList
 */
var NestedIterator = function (nestedList) {
    this.flattenedList = [];
    this.index = 0;
    
    const flatten = (list) => {
        for (const item of list) {
            if (item.isInteger()) {
                this.flattenedList.push(item.getInteger());
            } else {
                flatten(item.getList());
            }
        }
    };
    
    flatten(nestedList);
};

/**
 * @this NestedIterator
 * @returns {boolean}
 */
NestedIterator.prototype.hasNext = function () {
    return this.index < this.flattenedList.length;
};

/**
 * @this NestedIterator
 * @returns {integer}
 */
NestedIterator.prototype.next = function () {
    return this.flattenedList[this.index++];
};

/**
 * Your NestedIterator will be called like this:
 * var i = new NestedIterator(nestedList), a = [];
 * while (i.hasNext()) a.push(i.next());
 */