Peeking Iterator

Problem statement

Design an iterator that supports the peek operation on an existing iterator in addition to the hasNext and the next operations.

Implement the PeekingIterator class:

• PeekingIterator(Iterator<int> nums) Initializes the object with the given integer iterator iterator.
• int next() Returns the next element in the array and moves the pointer to the next element.
• boolean hasNext() Returns true if there are still elements in the array.
• int peek() Returns the next element in the array without moving the pointer.

Note: Each language may have a different implementation of the constructor and Iterator, but they all support the int next() and boolean hasNext() functions.

Example 1:

Input["PeekingIterator", "next", "peek", "next", "next", "hasNext"][[[1, 2, 3]], [], [], [], [], []]Output[null, 1, 2, 2, 3, false]ExplanationPeekingIterator peekingIterator = new PeekingIterator([1, 2, 3]); // [1,2,3]peekingIterator.next();    // return 1, the pointer moves to the next element [1,2,3].peekingIterator.peek();    // return 2, the pointer does not move [1,2,3].peekingIterator.next();    // return 2, the pointer moves to the next element [1,2,3]peekingIterator.next();    // return 3, the pointer moves to the next element [1,2,3]peekingIterator.hasNext(); // return False

Constraints:

• 1 <= nums.length <= 1000
• 1 <= nums[i] <= 1000
• All the calls to next and peek are valid.
• At most 1000 calls will be made to next, hasNext, and peek.

Follow up: How would you extend your design to be generic and work with all types, not just integer?

My solution

/**
 * // This is the Iterator's API interface.
 * // You should not implement it, or speculate about its implementation.
 * function Iterator() {
 *    @ return {number}
 *    this.next = function() { // return the next number of the iterator
 *       ...
 *    }; 
 *
 *    @return {boolean}
 *    this.hasNext = function() { // return true if it still has numbers
 *       ...
 *    };
 * };
 */

/**
 * @param {Iterator} iterator
 */
var PeekingIterator = function(iterator) {
     this.queue = [];
    
    while (iterator.hasNext()) {
        this.queue.push(iterator.next());
    }
};

/**
 * @return {number}
 */
PeekingIterator.prototype.peek = function() {
    return this.queue[0]
};

/**
 * @return {number}
 */
PeekingIterator.prototype.next = function() {
    return this.queue.shift()
};

/**
 * @return {boolean}
 */
PeekingIterator.prototype.hasNext = function() {
    return this.queue.length > 0
};

/** 
 * Your PeekingIterator object will be instantiated and called as such:
 * var obj = new PeekingIterator(arr)
 * var param_1 = obj.peek()
 * var param_2 = obj.next()
 * var param_3 = obj.hasNext()
 */