Next Greater Element I LeetCode solution in JavaScript

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/**
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 * @param {number[]} nums1
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 * @param {number[]} nums2
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 * @return {number[]}
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 */
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var nextGreaterElement = function (nums1, nums2) {
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  // [Value, Index] of all numbers in nums2
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  const indexMap = new Map();
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  for (let i = 0; i < nums2.length; i++) {
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    indexMap.set(nums2[i], i);
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  }
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  // Stores the next greatest elements
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  let result = [];
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  // Iterate through all the numbers of interest. Remember that all numbers in nums1 are present in nums2.
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  for (let num of nums1) {
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    // Check to see those numbers were present in the nums2 indexMap
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    if (indexMap.has(num)) {
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      // If they were, we must find the next greatest element.
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      // Set it to -1 by default in case we cannot find it.
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      let nextGreatest = -1;
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      // Iterate through all numbers in nums2 to the right of the index of the target number. (index of the target + 1)
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      for (let i = indexMap.get(num) + 1; i < nums2.length; i++) {
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        // Check to see if the current number is greater than the target.
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        if (nums2[i] > num) {
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          // If it is, this is the next greatest element.
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          nextGreatest = nums2[i];
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          // Break the loop.
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          break;
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        }
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      }
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      // Add the next greatest element (if found). Otherwise, add -1 (default)
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      result.push(nextGreatest);
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    }
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  }
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  // Return the array of next greatest elements.
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  return result;
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};