flatten a list / array in js

flatten.js

//input:  [[1], 2, [[3,4], 5], [[[]]], [[[6]]], 7, 8, []]

function flatten(list) {
  return list.reduce(function (acc, val) {
    return acc.concat(val.constructor === Array ? flatten(val) : val);
  }, []);
}

// output: [1, 2, 3, 4, 5, 6, 7, 8]

// more info: http://rosettacode.org/wiki/Flatten_a_list