Height Checker LeetCode solution in JavaScript

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var heightChecker = function (heights) {
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  let count = 0;
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  const orderedHeights = [...heights].sort((a, b) => a - b);
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  for (let i = 0; i < heights.length; i++) {
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    heights[i] !== orderedHeights[i] ? count++ : null;
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  }
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  return count;
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};