Minimum Swaps To Make Sequences Increasing LeetCode solution in JavaScript

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var minSwap = function (a, b) {
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  let n1 = 0,
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    s1 = 1,
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    len = a.length;
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  for (let i = 1; i < len; i++) {
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    let n2 = Number.MAX_VALUE,
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      s2 = Number.MAX_VALUE;
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    if (a[i - 1] < a[i] && b[i - 1] < b[i]) {
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      n2 = Math.min(n2, n1);
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      s2 = Math.min(s2, s1 + 1);
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    }
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    if (a[i - 1] < b[i] && b[i - 1] < a[i]) {
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      n2 = Math.min(n2, s1);
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      s2 = Math.min(s2, n1 + 1);
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    }
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    n1 = n2;
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    s1 = s2;
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  }
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  return Math.min(n1, s1);
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};