Swap rows with columns (transposition) of a matrix in javascript [duplicate]

Question

DuckDucking turned up this by Ken. Surprisingly, it’s even more concise and complete than Nikita’s answer. It retrieves column and row lengths implicitly within the guts of map().

function transpose(a) {
    return Object.keys(a[0]).map(function(c) {
        return a.map(function(r) { return r[c]; });
    });
}

console.log(transpose([
    [1,2,3],
    [4,5,6],
    [7,8,9]
]));

[[1,4,5],[2,5,8],[7,8,9]

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