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We're a place where coders share, stay up-to-date and grow their careers. # Day 22 of JavaScriptmas - Extract Matrix Column Solution Sekti
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Day 22 Challenge is to extract the specific column from a matrix (list of array).

For example, a matrix with `[[1, 1, 1, 2], [0, 5, 0, 4], [2, 1, 3, 6]]` which is has 3 index with 4 values/columns on each array.

If I draw it will be like this

``````[
[1, 1, 1, 2],
[0, 5, 0, 4],
[2, 1, 3, 6]
]
``````

Since this is list of array, if I want to extract ONLY the SECOND column (in this case the THIRD value because an array index always start at `0` index) that will give me an output `[1, 0, 3]`, I will use `.map`.

The way it works is, by looping the `matrix` using `.map`, it will return each array that I called it as `element`, and return the value of each `column` from the array using `element[column]`.

This is the JavaScript solution

``````function extractMatrixColumn(matrix, column) {
return matrix.map(element => element[column]);
}
``````

The test case

``````const matrix = [[1, 1, 1, 2], [0, 5, 0, 4], [2, 1, 3, 6]];
const column = 2;

extractMatrixColumn(matrix, column); // [1, 0, 3]
``````

## Discussion (2) Alfredo Salzillo 🐺
``````const extractMatrixColumn = (matrix, index) =>  {
return matrix.map(({ [index]: value }) => value);
}
`````` Sekti

Good one mate, you combine `.map` with destructuring assignment 👍