Minimum ASCII Delete Sum for Two Strings LeetCode solution in JavaScript

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var minimumDeleteSum = function (s1, s2) {
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  const len1 = s1.length,
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    len2 = s2.length;
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  const dp = [...Array(len1 + 1)].map(() => Array(len2 + 1).fill(0));
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  for (let i = 1; i <= len1; i++) {
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    dp[i][0] = dp[i - 1][0] + s1.charCodeAt(i - 1);
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  }
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  for (let j = 1; j <= len2; j++) {
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    dp[0][j] = dp[0][j - 1] + s2.charCodeAt(j - 1);
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  }
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  for (let i = 1; i <= len1; i++) {
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    for (let j = 1; j <= len2; j++) {
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      if (s1[i - 1] == s2[j - 1]) dp[i][j] = dp[i - 1][j - 1];
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      else {
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        const del1 = s1.charCodeAt(i - 1) + dp[i - 1][j];
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        const del2 = s2.charCodeAt(j - 1) + dp[i][j - 1];
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        dp[i][j] = Math.min(del1, del2);
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      }
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    }
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  }
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  return dp[len1][len2];
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};