LeetCode: Peeking Iterator Solution

1/**
2 * // This is the Iterator's API interface.
3 * // You should not implement it, or speculate about its implementation.
4 * function Iterator() {
5 *    @ return {number}
6 *    this.next = function() { // return the next number of the iterator
7 *       ...
8 *    };
9 *
10 *    @return {boolean}
11 *    this.hasNext = function() { // return true if it still has numbers
12 *       ...
13 *    };
14 * };
15 */
16
17/**
18 * @param {Iterator} iterator
19 */
20var PeekingIterator = function (iterator) {
21  this.stack = []
22  while (iterator.hasNext()) {
23    this.stack.unshift(iterator.next())
24  }
25}
26
27/**
28 * @return {number}
29 */
30PeekingIterator.prototype.peek = function () {
31  return this.stack[this.stack.length - 1]
32}
33
34/**
35 * @return {number}
36 */
37PeekingIterator.prototype.next = function () {
38  return this.stack.pop()
39}
40
41/**
42 * @return {boolean}
43 */
44PeekingIterator.prototype.hasNext = function () {
45  return this.stack.length !== 0
46}
47
48/**
49 * Your PeekingIterator object will be instantiated and called as such:
50 * var obj = new PeekingIterator(arr)
51 * var param_1 = obj.peek()
52 * var param_2 = obj.next()
53 * var param_3 = obj.hasNext()
54 */