Javascript Array Intersection

// https://leetcode.com/problems/intersection-of-two-arrays/
var intersection = function (nums1, nums2) {
    var hash = {};
    var arrayIntersect = [];
    var lengthNums1 = nums1.length;
    var lengthNums2 = nums2.length;
    for (var i = 0; i < lengthNums1; i++) {
        hash[nums1[i]] = 1; // cannot use 0 because 0 and undefined are the same.
    }/* www.  ja v a2s.c o  m*/
    //console.log(hash);
    for (var i = 0; i < lengthNums2; i++) {
        if (hash[nums2[i]] && (hash[nums2[i]] === 1)) {
            arrayIntersect.push(nums2[i]);
            hash[nums2[i]]++;
        }
    }
    return arrayIntersect;
};
console.log(intersection([1, 2, 2, 1], [2, 2]));

// https://leetcode.com/problems/intersection-of-two-arrays-ii/
// version 2 - allow duplicates
var intersect = function (nums1, nums2) {
    var hash = {};
    var arrayIntersect = [];
    var lengthNums1 = nums1.length;
    var lengthNums2 = nums2.length;
    for (var i = 0; i < lengthNums1; i++) {
        hash[nums1[i]] = (!hash[nums1[i]]) ? 1 : (hash[nums1[i]] + 1); // cannot use 0 because 0 and undefined are the same.
    }/*from  w w  w .  jav  a2  s.  c o m*/
    //console.log(hash);
    for (var i = 0; i < lengthNums2; i++) {
        if (hash[nums2[i]] && (hash[nums2[i]] > 0)) {
            arrayIntersect.push(nums2[i]);
            hash[nums2[i]]--;
        }
    }
    return arrayIntersect;
};
console.log(intersect([1, 2, 2, 1, 2, 2], [2, 2, 2]));