How to pair elements between multiple arrays in javascript

Question

I have a multidimensional array which can contain a different number of arrays. What I want to do is to match all arrays in order of key not value, and produce a new array for each row created, something like this

var arr = [
  [1,2,3,4,5],
  [1,2,3,4,5],
  [1,2,3,4,5],
  [1,2,3,4,5]
]

The result I need

var arr = [[1,1,1,1],[2,2,2,2],[3,3,3,3],[4,4,4,4],[5,5,5,5]]

how can I achieve this?

Do you mean convert rows into columns and columns into rows? — KapilDev Neupane, Feb 28 '18 at 04:31
through the use of code ... have at it then come back when you're stuck :p — Jaromanda X, Feb 28 '18 at 04:31
`const rotate = a => Object.keys(a[0]).map(c => a.map(r => r[c] ));` - oh, wait, you don't want to rotate the array, you just want an array of arrays of the same value? — Jaromanda X, Feb 28 '18 at 04:36
your sample input and output are actually ambiguous ... what if the input is `[[1,2,3],[4,5,6],[7,8,9]]` what output would you expect? — Jaromanda X, Feb 28 '18 at 04:49
Or better yet `const fn=a=>a[0].map((c, i)=>a.map(r=>r[i]));` — Jaromanda X, Feb 28 '18 at 04:57

score 1 · Answer 1 · answered Feb 28 '18 at 04:36

1

I think here is what you are looking for.

var arr = [
  [1,2,3,4,5],
  [1,2,3,4,5],
  [1,2,3,4,5],
  [1,2,3,4,5]
];

var res = arr.reduce((x, y) => {
  for(let i in y) {
    x[i] ? x[i].push(y[i]) : x[i] = [y[i]];
  }
  
  return x;
}, []);

console.log(res);

answered Feb 28 '18 at 04:36

Shubham

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nevermind my comment :p – Jaromanda X Feb 28 '18 at 04:48
@JaromandaX He wants in order of keys not values. His query was "**I want to do is to match all arrays in order of key not value**" – Shubham Feb 28 '18 at 04:56
I misread your code :p – Jaromanda X Feb 28 '18 at 04:57

Sai Manoj · Answer 2 · 2018-02-28T04:56:59.877

I hope that you are looking for this one. It retrieves column and row lengths implicitly within the map(). Source [Swap rows with columns (transposition) of a matrix in javascript

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],
      [1,2,3,4,5],
      [1,2,3,4,5],
      [1,2,3,4,5]
        ]));

How to pair elements between multiple arrays in javascript

2 Answers2