Longest Harmonious Subsequence LeetCode solution in JavaScript

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var findLHS = function (nums) {
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  let countNumber = {};
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  let result = [];
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  for (let i = 0; i < nums.length; i++) {
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    if (!countNumber[nums[i]]) {
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      countNumber[nums[i]] = 1;
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    } else {
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      countNumber[nums[i]]++;
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    }
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  }
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  for (let value of Object.keys(countNumber)) {
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    let count;
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    let current = parseInt(value);
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    if (countNumber[current + 1]) {
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      count = countNumber[current] + countNumber[current + 1];
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      result.push(count);
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    }
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  }
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  if (result.length === 0) {
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    return 0;
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  }
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  return Math.max(...result);
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};