Filling Bookcase Shelves LeetCode solution in JavaScript

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var minHeightShelves = function (books, shelfWidth) {
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  let booksArr = [];
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  for (let i = 0; i < books.length; i++) {
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    let remainingWidth = shelfWidth - books[i][0];
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    let bookHeight = books[i][1];
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    let maxHeight = bookHeight;
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    let prevSum = booksArr[i - 1] !== undefined ? booksArr[i - 1] : 0;
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    let minSumHeight = bookHeight + prevSum;
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    for (let x = i - 1; x >= 0; x--) {
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      let prevBookWidth = books[x][0];
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      let prevBookHeight = books[x][1];
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      if (remainingWidth - prevBookWidth < 0) break;
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      remainingWidth -= prevBookWidth;
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      prevSum = booksArr[x - 1] !== undefined ? booksArr[x - 1] : 0;
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      maxHeight = Math.max(maxHeight, prevBookHeight);
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      minSumHeight = Math.min(prevSum + maxHeight, minSumHeight);
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    }
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    booksArr[i] = minSumHeight;
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  }
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  return booksArr[books.length - 1];
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};