Fraction to Recurring Decimal LeetCode solution in JavaScript

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var fractionToDecimal = function (numerator, denominator) {
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  if (numerator == 0) return "0";
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  let result = "";
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  if (numerator * denominator < 0) {
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    result += "-";
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  }
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  let dividend = Math.abs(numerator);
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  let divisor = Math.abs(denominator);
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  result += Math.floor(dividend / divisor).toString();
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  let remainder = dividend % divisor;
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  if (remainder == 0) return result;
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  result += ".";
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  let map1 = new Map();
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  while (remainder != 0) {
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    if (map1.has(remainder)) {
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      let i = map1.get(remainder);
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      result = result.slice(0, i) + "(" + result.slice(i) + ")";
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      break;
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    }
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    map1.set(remainder, result.length);
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    remainder *= 10;
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    result += Math.floor(remainder / divisor).toString();
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    remainder %= divisor;
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  }
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  return result;
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};