Minimum Number of Flips to Make the Binary String Alternating LeetCode solution in JavaScript

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/**
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 * @param {string} s
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 * @return {number}
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 */
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var minFlips = function (s) {
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  let length = s.length - 1;
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  let flipMap = {
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    1: "0",
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    0: "1",
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  };
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  s = s + s;
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  let alt1 = "1";
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  let alt2 = "0";
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  let left = 0;
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  let right = 0;
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  let diff1 = 0;
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  let diff2 = 0;
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  let min = Infinity;
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  while (right < s.length) {
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    if (right > 0) {
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      alt1 = flipMap[alt1];
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      alt2 = flipMap[alt2];
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    }
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    let current = s[right];
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    if (current !== alt1) diff1++;
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    if (current !== alt2) diff2++;
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    if (right - left === length) {
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      min = Math.min(diff1, diff2, min);
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      if ((length + 1) % 2 === 0) {
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        if (s[left] !== flipMap[alt1]) diff1--;
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        if (s[left] !== flipMap[alt2]) diff2--;
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      } else {
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        if (s[left] !== alt1) diff1--;
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        if (s[left] !== alt2) diff2--;
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      }
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      left++;
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    }
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    right++;
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  }
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  return min;
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};