How to parse array of multiple arrays

Question

I am trying to change an array which contains multiple arrays into a form that I can use for an external API.

Example:

[ [44.5,43.2,45.1] , [42, 41.2, 48.1] ]

into

[ [44.5,42], [43.2,41.2] , [45.1, 48.1] ]

Currently my code runs as this, but doesn't work

var newArr= [];
var tempArr= [];

for(var key in data){
    tempArr.push(finalArr[key][key])
    newArr.push(tempArr)
 }

Is there some easier way to accomplish this without looping? I was thinking of maybe a map function but I'm not sure how to implement it here.

Are you always going to have an array with exactly two sub-arrays? — sassy_rog
– sassy_rog, Commented Apr 19, 2019 at 19:21
"without looping" — anytime you have a list of things, something has to iterate ("loop") through the list items. There's no escaping it. — Pointy
– Pointy, Commented Apr 19, 2019 at 19:23

Nina Scholz · Accepted Answer · 2019-04-19 19:23:10Z

2

You could transpose the arrays by reducing and mapping the values.

This works for any length.

const transpose = array => array.reduce((r, a) => a.map((v, i) => [...(r[i] || []), v]), []);

console.log(transpose([[44.5, 43.2, 45.1], [42, 41.2, 48.1]]));

.as-console-wrapper { max-height: 100% !important; top: 0; }

answered Apr 19, 2019 at 19:23

Nina Scholz

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1 Comment

mrDinckleman Over a year ago

Very cool solution but, I afraid, to the detriment of readability

mrDinckleman · Accepted Answer · 2019-04-19 19:41:19Z

1

var arr = [
  [44.5, 43.2, 45.1],
  [42, 41.2, 48.1]
];
var result = arr[0].map(function (el, index) {
  return [el, arr[1][index]];
});
console.log(result);

But you have to be sure, that source arrays have same length.

edited Apr 19, 2019 at 19:41

answered Apr 19, 2019 at 19:22

mrDinckleman

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1 Comment

James Over a year ago

return arr.map(b => b[index]); to generalize it to n arrays.

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