Flattening an Array of array of array of ..... arrays.

flatten.js

var assert = require('assert');
/**
 * Flattens array that are nested at n levels.
 * @param  {Array} arr The array to be flattened
 * @return {Array}     New array with flattened elements.
 * ----------------------------------------------------------
 */
 function flatten(arr) {
  if(!arr) {
    return [];
  }
   return arr.reduce((c,v) => {
     if(Array.isArray(v)){
       return c.concat(flatten(v));
     }
     return c.concat(v);
   }, []);
 }


var case0 = [];
var case1 = [[[[[[[[[[[[[[[[[[[[1]]]]]]]]]]]]]]]]]]], 2];
var case2 = [1, [2], [[3]], [4,[[5, [6]], [7]],[[[8]]]], 9, [10]];
var caseNull = null;

assert.deepEqual(flatten(case0), []);
assert.deepEqual(flatten(case1), [1,2]);
assert.deepEqual(flatten(case2), [1,2,3,4,5,6,7,8,9,10]);
assert.deepEqual(flatten(caseNull), []);