function extractMatrixColumn(matrix, column) {
    let retArray = [];

    // if the matrix is a valid one
    let matrixRowLength = matrix[0].length;
    for (let i = 0; i < matrix.length; i++) {
        if (matrix[i].length != matrixRowLength) {
            return retArray;
        }
    }
    
    //the the required column exists
    if (column < matrix[0].length) {
        for (let i = 0; i < matrix.length; i++) {
            retArray.push(matrix[i][column]);
        }
    }
    return retArray;
}



/**
* Test Suite 
*/
describe('extractMatrixColumn()', () => {
    it('returns largest positive integer possible for digit count', () => {
        // arrange
        const matrix = [[1, 1, 1, 2], [0, 5, 0, 4], [2, 1, 3, 6]];
        const column = 2;

        // act
        const result = extractMatrixColumn(matrix, column);

        // log
        console.log("result: ", result);

        // assert
        expect(result).toEqual([1, 0, 3]);
    });
});


describe('extractMatrixColumn()', () => {
    it('returns largest positive integer possible for digit count', () => {
        // arrange
        const matrix = [[1, 1, 1, 3], [0, 3, 4, 4], [2, 6, 5, 6]];
        const column = 3;

        // act
        const result = extractMatrixColumn(matrix, column);

        // log
        console.log("result: ", result);

        // assert
        expect(result).toEqual([3, 4, 6]);
    });
});

describe('extractMatrixColumn()', () => {
    it('return empty array because the matrix is invalid', () => {
        // arrange
        const matrix = [[1, 1, 1], [0, 3, 4, 4], [2, 2, 6, 5, 6]];
        const column = 3;

        // act
        const result = extractMatrixColumn(matrix, column);

        // log
        console.log("result: ", result);

        // assert
        expect(result).toEqual([]);
    });
});

describe('extractMatrixColumn()', () => {
    it('return empty array requested columnt doesnt exists', () => {
        // arrange
        const matrix = [[1, 1, 1,5], [0, 3, 4,4], [0, 3, 7,4]];
        const column = 9;

        // act
        const result = extractMatrixColumn(matrix, column);

        // log
        console.log("result: ", result);

        // assert
        expect(result).toEqual([]);
    });
});