Number of Substrings With Only 1s LeetCode solution in JavaScript

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var numSub = function (s) {
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  return (
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    s
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      .split("0")
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      .map((a) => (a.length * (a.length + 1)) / 2)
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      .reduce((a, b) => a + b, 0) % 1000000007
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  );
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};