Maximize Score After N Operations LeetCode solution in JavaScript

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var maxScore = function (nums) {
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  function gcd(a, b) {
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    if (!b) return a;
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    return gcd(b, a % b);
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  }
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  const memo = new Map();
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  function recurse(arr, num1, op) {
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    if (!arr.length) return 0;
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    const key = arr.join() + num1;
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    if (memo.has(key)) return memo.get(key);
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    let max = 0;
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    for (let i = 0; i < arr.length; i++) {
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      const nextArr = [...arr.slice(0, i), ...arr.slice(i + 1)];
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      if (num1) {
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        const currGCD = gcd(num1, arr[i]);
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        const rest = recurse(nextArr, null, op + 1);
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        max = Math.max(max, op * currGCD + rest);
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      } else {
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        const rest = recurse(nextArr, arr[i], op);
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        max = Math.max(max, rest);
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      }
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    }
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    memo.set(key, max);
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    return max;
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  }
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  return recurse(nums, null, 1);
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};