How Can I Efficiently Transpose a 2D Array in JavaScript?

Transposing a 2D-array with JavaScript's Condensed Syntax

Transposing a 2D array involves converting rows into columns and vice versa. While basic loop-based solutions exist, JavaScript offers a more concise approach that leverages functional programming techniques.

Consider the provided 2D array:

[
    [1, 2, 3],
    [1, 2, 3],
    [1, 2, 3],
]

The concise transposition using map() can be expressed as:

output = array[0].map((_, colIndex) => array.map(row => row[colIndex]));

Breaking down the code:

1. array[0].map: Iterates over the first row of the original array.
2. (_, colIndex): As the outer map iterates through empty elements, the underscore (_) placeholder is used instead of an actual value. colIndex represents the column index.
3. array.map: For each column index, this inner map iterates through the original array.
4. row => row[colIndex] : Extracts the element in the specified column for each row.

The result is a new 2D array where each row in the original array has become a column in the transposed array:

[
    [1, 1, 1],
    [2, 2, 2],
    [3, 3, 3],
]

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