supernoveau · May 25, 2016 16:29
diff --git a/flatten.js b/flatten.js
 function flatten(arr) {
  return arr.reduce( (flat, toFlatten) => {
    return flat.concat(Array.isArray(toFlatten) ? flatten(toFlatten) : toFlatten);
  }, []);
 }

 console.log( flatten([[1,2,[3]],4]) );
	function flatten(arr) {
	return arr.reduce( (flat, toFlatten) => {
	return flat.concat(Array.isArray(toFlatten) ? flatten(toFlatten) : toFlatten);
	}, []);
	}

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