Longest Uncommon Subsequence II LeetCode solution in JavaScript

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var findLUSlength = function (strs) {
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  strs.sort((a, b) => b.length - a.length);
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  const isSubsequence = (a, b) => {
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    const A_LENGTH = a.length;
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    const B_LENGTH = b.length;
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    if (A_LENGTH > B_LENGTH) return false;
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    if (a === b) return true;
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    const matches = [...b].reduce((pos, str) => {
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      return a[pos] === str ? pos + 1 : pos;
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    }, 0);
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    return matches === A_LENGTH;
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  };
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  for (let a = 0; a < strs.length; a++) {
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    let isUncommon = true;
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    for (let b = 0; b < strs.length; b++) {
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      if (a === b) continue;
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      if (isSubsequence(strs[a], strs[b])) {
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        isUncommon = false;
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        break;
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      }
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    }
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    if (isUncommon) return strs[a].length;
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  }
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  return -1;
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};