Group an array to form three arrays based on the index

Question

I want to sort an array in a way that it gives back three arrays. So

var myArray = [\'1\',\'2\',\'3\',\'1\',\'2\',\'3\',\'1\',\'2\',\'3\',\'1\',\'2\',\'3\',\'1\'         


        

Answer 1

var myArray = ['1','2','3','1','2','3','1','2','3','1','2','3','1','2','3','1','2','3','1','2','3','1','2','3','1','2','3','1','2','3','1','2','3','1','2','3','1','2','3','1','2','3','1','2','3','1','2','3','1','2','3','1','2','3'];

var myArray1 = [];
var myArray2 = [];
var myArray3 = [];
for(var i = 0; i < myArray.length;) {
    myArray1.push(myArray [i++]); 
    myArray2.push(myArray [i++]);
    myArray3.push(myArray [i++]);
}

Answer 2

You could create a generic function which will group the array based on the n provided. Based on the result of index % n, push them into specific arrays. Here, n = 3. If you use i % 2, this will distribute the numbers into 2 arrays based on odd and even indices.

const myArray = ['1', '2', '3', '1', '2', '3', '1', '2', '3', '1', '2', '3', '1', '2', '3', '1', '2', '3', '1', '2', '3', '1', '2', '3', '1', '2', '3', '1', '2', '3', '1', '2', '3', '1', '2', '3', '1', '2', '3', '1', '2', '3', '1', '2', '3', '1', '2', '3', '1', '2', '3', '1', '2', '3'];

function group(array, n) {
  return myArray.reduce((acc, number, i) => {
    acc[i % n] = acc[i % n] || [];
    acc[i % n].push(number);
    return acc;
  }, [])
}

const grouped = group(myArray, 3);

console.log(JSON.stringify(grouped[0]))
console.log(JSON.stringify(grouped[1]))
console.log(JSON.stringify(grouped[2]))

Answer 3

If you're looking for high-order solution (using methods, like Array.prototype.reduce()) following approach might work:

const arr = ['1','2','3','1','2','3','1','2','3','1','2','3','1','2','3','1','2','3','1','2','3','1','2','3','1','2','3','1','2','3','1','2','3','1','2','3','1','2','3','1','2','3','1','2','3','1','2','3','1','2','3','1','2','3'];

const [arr1,arr2,arr3] = arr.reduce((res,e,i) => (res[i%3].push(e),res), [[],[],[]]);

console.log(`arr1 = ${JSON.stringify(arr1)}`);
console.log(`arr2 = ${JSON.stringify(arr2)}`);
console.log(`arr3 = ${JSON.stringify(arr3)}`);

.as-console-wrapper{min-height:100%}

p.s. got a sneak peek at this (universal) solution to make mine a bit more compact