Find Substring With Given Hash Value LeetCode solution in JavaScript

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let arrChar = "1abcdefghijklmnopqrstuvwxyz".split("");
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var subStrHash = function (s, power, modulo, k, hashValue) {
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  for (let i = 0; i < s.length; i++) {
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    let subStr = s.substring(i, i + k);
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    if (hash(subStr, power, modulo) == hashValue) {
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      return subStr;
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    }
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  }
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};
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let hash = function (str, power, m) {
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  let result = 0;
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  for (let i = 0; i < str.length; i++) {
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    result += arrChar.indexOf(str[i]) * Math.pow(power, i);
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  }
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  return result % m;
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};