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var isPalindrome = function (x) {
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  if (x < 0 || (x % 10 === 0 && x !== 0)) return false;
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  let num = x;
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  let rev_x = 0;
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  while (x > 0) {
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    let digit = Math.floor(x % 10);
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    rev_x = Math.floor(rev_x * 10 + digit);
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    x = Math.floor(x / 10);
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  }
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  return num === rev_x;
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};