Concatenation of Consecutive Binary Numbers LeetCode solution in JavaScript

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var concatenatedBinary = function (n) {
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  let num = 0;
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  for (let i = 1; i <= n; i++) {
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    //OR num *= (1 << i.toString(2).length)
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    num *= 2 ** i.toString(2).length;
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    num += i;
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    num %= 10 ** 9 + 7;
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  }
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  return num;
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};