Bitwise ORs of Subarrays LeetCode solution in JavaScript

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/** https://leetcode.com/problems/bitwise-ors-of-subarrays/
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 * @param {number[]} arr
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 * @return {number}
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 */
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var subarrayBitwiseORs = function (arr) {
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  // Hashset to store the unique bitwise
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  this.uniqueBw = new Set();
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  // Dynamic programming
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  dp(arr, arr.length - 1);
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  return this.uniqueBw.size;
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};
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var dp = function (arr, currIdx) {
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  // Base, reach beginning of the array
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  if (currIdx === 0) {
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    // Store the value to unique bitwise, since it's only single number, we store the actual value
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    this.uniqueBw.add(arr[0]);
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    // Return array
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    return [arr[0]];
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  }
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  // DP to previous index
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  let prev = dp(arr, currIdx - 1);
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  // Number at current index
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  let firstBw = arr[currIdx];
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  // Add number at current index to hashset, since it's only single number, we store the actual value
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  this.uniqueBw.add(firstBw);
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  // Another hashset to store the result of bitwise operation between number at current index with result from previous index
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  let currRes = new Set();
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  currRes.add(firstBw);
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  // Loop through result form previous index
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  for (let i = 0; i < prev.length; i++) {
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    // Perform bitwise operation OR
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    let curr = arr[currIdx] | prev[i];
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    // Add to unique bitwise collection
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    this.uniqueBw.add(curr);
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    // Add to current result
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    currRes.add(curr);
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  }
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  // Return current result as an array
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  return [...currRes];
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};