How to loop OVER several arrays

Question

I have n number of arrays. Same amount of rows in each of them: Array0, Array1, ..., Arrayn.

Now I want to loop through all of them and ultimately join them. Transpose each Array to a column of the new created ResultArray

for (var ID = 0; ID < n+1; ID++) {
    for (var i = 0; i < ("Array" + ID).length; i++) {
      ResultArray[i][ID] = ("Array" + ID)[i]
        }
  }

Here is an example of what I want:

Array0 = [Apple, Banana, Chicken]
Array1 = [5, 7, 8]
Array2 = [High, Low, Low]
ResultArray = [[Apple, 5, High], [Banana, 7, Low], [Chicken, 8, Low]]

Tanaike · Accepted Answer · 2019-06-13 03:32:00Z

2

You have the following arrays.

    Array0 = ["Apple", "Banana", "Chicken"];
    Array1 = [5, 7, 8];
    Array2 = ["High", "Low", "Low"];

You want to convert above arrays to the following array.

    [["Apple",5,"High"],["Banana",7,"Low"],["Chicken",8,"Low"]]

From your sample array, the array length of each array is the same.

If my understanding is correct, how about this modification? Please think of this as just one of several answers.

Modified script 1:

var Array0 = ["Apple", "Banana", "Chicken"];
var Array1 = [5, 7, 8];
var Array2 = ["High", "Low", "Low"];

var arrays = [Array0, Array1, Array2]; // Please prepare this.

var res = [];
for (var i = 0; i < arrays[0].length; i++) {
  var temp = [];
  for (var j = 0; j < arrays.length; j++) {
    var ar = arrays[j];
    temp.push(ar[i]);
  }
  res.push(temp);
}
Logger.log(res)

Modified script 2:

var Array0 = ["Apple", "Banana", "Chicken"];
var Array1 = [5, 7, 8];
var Array2 = ["High", "Low", "Low"];

var numberOfArrays = 3; // Please prepare this. In your case, it's 3.

var res = [];
for (var i = 0; i < Array0.length; i++) {
  var temp = [];
  for (var j = 0; j < numberOfArrays; j++) {
    var ar = eval("Array" + j);
    temp.push(ar[i]);
  }
  res.push(temp);
}
Logger.log(res)

Note:

Please select one of above scripts for your situation.

If I misunderstood your question and this was not the result you want, I apologize.

answered Jun 13, 2019 at 3:32

Tanaike

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2 Comments

Kibou Over a year ago

Wonderful! :) Used 'Modified script 1' and it works perfect!

Tanaike Over a year ago

@Kibou Thank you for replying. I'm glad your issue was resolved.

Akrion · Accepted Answer · 2019-06-13 16:54:59Z

You can also solve this in a more concise way with Array.reduce:

const arr1 = ["Apple", "Banana", "Chicken"], arr2 = [5, 7, 8], arr3 = ["High", "Low", "Low"],
      data = [arr1, arr2, arr3]

let result = data.reduce((acc, c) => 
 (c.forEach((x,k) => acc[k].push(x)), acc), Array.from({length: data.length}, () => []))

console.log(result)

Or in a more readable form:

const arr1 = ["Apple", "Banana", "Chicken"], arr2 = [5, 7, 8], arr3 = ["High", "Low", "Low"],
      data = [arr1, arr2, arr3]

let result = data.reduce((acc, c) => {
  c.forEach((x,i) => acc[i].push(x))
  return acc
}, Array.from({length: data.length}, () => []))

console.log(result)

The idea is to merge those arrays and then do Array.reduce where the accumulator is already in the form of [[],[],[]] so we just populate each of the child arrays.

Ori Drori · Accepted Answer · 2019-06-14 11:16:18Z

0

Use Array.reduce() to find the longest array. Use Array.map() to iterate the longest array, and get the row index. Then use a second Array.map() to get the row items from the arrays.

const zip = (...arrs) => arrs
  .reduce((r, c) => c.length > r.length ? c : r, []) // get the longest array
  .map((_, i) => arrs.map(a => a[i])) // map the longest array to get the current row number, then create the row

const arr1 = ["Apple", "Banana", "Chicken"], arr2 = [5, 7, 8], arr3 = ["High", "Low", "Low"]

const result = zip(arr1, arr2, arr3)

console.log(result)

answered Jun 14, 2019 at 11:16

Ori Drori

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How to loop OVER several arrays

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