Flatten a Nested Array

flatten.js

/* flatten function
	 Accepts an n-dimensional array
    as an argument and returns a
    1-dimensional array
   Returns value for non-arrays
   Uses recursion to drill down
    into each array section
*/
function flatten(val) {
	// if not an array returns value
	if (!(Array.isArray(val))) return val;
  // call reduce starting with an empty array
	return val.reduce((acc, curr) => {
    // recursive flattening of each element
    return acc.concat(flatten(curr));
  }, []);
}

// testing
//console.log(flatten([[1,2,[3]],4]);