Interleaving String LeetCode solution in JavaScript

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var isInterleave = function (s1, s2, s3) {
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  const dp = new Map();
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  const solve = (a = 0, b = 0, c = 0) => {
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    if (c == s3.length) return a == s1.length && b == s2.length;
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    const key = [a, b, c].join(":");
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    if (dp.has(key)) {
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      // console.log('hit');
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      return dp.get(key);
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    }
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    let takeS1 = false,
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      takeS2 = false;
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    if (s1[a] == s3[c]) takeS1 = solve(a + 1, b, c + 1);
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    if (s2[b] == s3[c]) takeS2 = solve(a, b + 1, c + 1);
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    dp.set(key, takeS1 || takeS2);
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    return takeS1 || takeS2;
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  };
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  return solve();
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};