Flatten array using recursion.

[Ashwin7mak]

We can flatten multi dimensional array using recursion in this way.

const flatten_array = arr => {
// Concat given array with an empty array
let flatten = [].concat(...arr);
// Check if the flatten array contains any further array
// If so do recursion of that array else return the array
return flatten.some(Array.isArray) ? flatten_array(flatten) : flatten;
}

[rohan-paul]

that looks nice and compact. Thanks @Ashwin7mak