Split array into chunks of N length [duplicate]

Question

How to split an array (which has 10 items) into 4 chunks, which contain a maximum of n items.

var a = ['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j'];
//a function splits it to four arrays.
console.log(b, c, d, e);

And it prints:

['a', 'b', 'c']
['d', 'e', 'f']
['j', 'h', 'i']
['j']

The above assumes n = 3, however, the value should be dynamic.

Thanks

Answer 1

It could be something like that:

var a = ['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j'];

var arrays = [], size = 3;
    
while (a.length > 0)
  arrays.push(a.splice(0, size));

console.log(arrays);

See splice Array's method.

An alternative method that does not mutate the array, beside create a shallow copy of it before chunk it, could be done by using slice and a for…loop:

var a = ['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j'];

var arrays = [], size = 3;
    
for (let i = 0; i < a.length; i += size)
   arrays.push(a.slice(i, i + size));

console.log(arrays);

While a more functional programming oriented approach, could be:

const chunks = (a, size) =>
    Array.from(
        new Array(Math.ceil(a.length / size)),
        (_, i) => a.slice(i * size, i * size + size)
    );

let a = ['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j'];

console.log(chunks(a, 3));
console.log(chunks(a, 2));

See Array.from and how new Array(n) works, specifically.

Answer 2

Maybe this code helps:

var chunk_size = 10;
var arr = [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17];
var groups = arr.map( function(e,i){ 
     return i%chunk_size===0 ? arr.slice(i,i+chunk_size) : null; 
}).filter(function(e){ return e; });
console.log({arr, groups})