Flatten Nested List Iterator.js

/**
Given a nested list of integers, implement an iterator to flatten it.

Each element is either an integer, or a list -- whose elements may also be integers or other lists.

Example 1:
Given the list [[1,1],2,[1,1]],

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

Example 2:
Given the list [1,[4,[6]]],

By calling next repeatedly until hasNext returns false, the order of elements returned by next should be: [1,4,6].
*/
/**
 * // 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.stack = nestedList.reverse();
};


/**
 * @this NestedIterator
 * @returns {boolean}
 */
NestedIterator.prototype.hasNext = function() {
    var next,
        i;
    
    while (this.stack.length > 0) {
        next = this.stack[this.stack.length - 1];
        
        if (next.isInteger()) {
            return true;
        }
        
        this.stack.pop();
        
        for (i = next.getList().length - 1; i >= 0; i--) {
            this.stack.push(next.getList()[i]);
        }
    }
    
    return false;
};

/**
 * @this NestedIterator
 * @returns {integer}
 */
NestedIterator.prototype.next = function() {
    return this.stack.pop();
};

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