LeetCode 217. Contains Duplicate (javascript solution)

Description:

Given an integer array nums, return true if any value appears at least twice in the array, and return false if every element is distinct.

Solution:

Time Complexity : O(n)
Space Complexity: O(n)

var containsDuplicate = function(nums) {
    const map = {}
    for(const num of nums) {
        // If we have seen this num before return true
        if(map[num]) return true
        map[num] = true
    }
    return false
};