Longest Valid Parentheses LeetCode solution in JavaScript

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var longestValidParentheses = function (s) {
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  let indexStack = [-1];
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  let characterStack = [];
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  let maxLength = 0;
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  for (let i = 0; i < s.length; i++) {
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    if (s[i] == "(") {
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      indexStack.push(i);
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      characterStack.push(s[i]);
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    } else {
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      if (characterStack[characterStack.length - 1] == "(") {
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        indexStack.pop();
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        characterStack.pop();
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        if (maxLength < i - indexStack[indexStack.length - 1]) {
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          maxLength = i - indexStack[indexStack.length - 1];
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        }
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      } else {
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        indexStack.push(i);
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      }
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    }
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  }
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  return maxLength;
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};