Flatten Nested List Iterator

Problem statement

You are given a nested list of integers nestedList. Each element is either an integer or a list whose elements may also be integers or other lists. Implement an iterator to flatten it.

Implement the NestedIterator class:

NestedIterator(List<NestedInteger> nestedList) Initializes the iterator with the nested list nestedList.
int next() Returns the next integer in the nested list.
boolean hasNext() Returns true if there are still some integers in the nested list and false otherwise.

Your code will be tested with the following pseudocode:

initialize iterator with nestedListres = []while iterator.hasNext()    append iterator.next() to the end of resreturn res

If res matches the expected flattened list, then your code will be judged as correct.

Example 1:

Input: nestedList = [[1,1],2,[1,1]]Output: [1,1,2,1,1]Explanation: By calling next repeatedly until hasNext returns false, the order of elements returned by next should be: [1,1,2,1,1].

Example 2:

Input: nestedList = [1,[4,[6]]]Output: [1,4,6]Explanation: By calling next repeatedly until hasNext returns false, the order of elements returned by next should be: [1,4,6].

Constraints:

1 <= nestedList.length <= 500
The values of the integers in the nested list is in the range [-10⁶, 10⁶].

My solution

/**
 * // 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.list = nestedReduce(nestedList)
    
    // console.log(this.list)
};

function nestedReduce(nestedList){
    return [...nestedList].reduce((acc, curr) => {
        const isList = !curr.isInteger();
        if (isList) {
            acc = [...acc, ...nestedReduce(curr.getList())]
        } else {
           acc.push(curr.getInteger()) 
        }
        return acc;
    }, [])
}


/**
 * @this NestedIterator
 * @returns {boolean}
 */
NestedIterator.prototype.hasNext = function() {
    return this.list.length > 0
};

/**
 * @this NestedIterator
 * @returns {integer}
 */
NestedIterator.prototype.next = function() {
    const value = this.list.shift();
    return typeof value === "number" ? value : value.getInteger()
};

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

Flatten Nested List Iterator

Problem statement​

My solution​

Problem statement

My solution