[LeetCode][JavaScript]Contains Duplicate II

Contains Duplicate II 

Given an array of integers and an integer k, return true if and only if there are two distinct indices i and j in the array such that nums[i] = nums[j] and the difference between i and j is at most k.

https://leetcode.com/problems/contains-duplicate-ii/

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数组中两个相同值的数，下标之差要小于等于k。

/**
 * @param {number[]} nums
 * @param {number} k
 * @return {boolean}
 */
var containsNearbyDuplicate = function(nums, k) {
    var map = {};
    for(var i in nums){
        if(map[nums[i]]){
            if(Math.abs(map[nums[i]] - i) <= k){
                return true;
            }
        }
        map[nums[i]] = i;
    }
    return false;
};