Dividing an array by filter function

Question

I have a Javascript array that I would like to split into two based on whether a function called on each element returns true or false. Essentially

Answer 1

You can use lodash.partition

var users = [
  { 'user': 'barney',  'age': 36, 'active': false },
  { 'user': 'fred',    'age': 40, 'active': true },
  { 'user': 'pebbles', 'age': 1,  'active': false }
];

_.partition(users, function(o) { return o.active; });
// → objects for [['fred'], ['barney', 'pebbles']]

// The `_.matches` iteratee shorthand.
_.partition(users, { 'age': 1, 'active': false });
// → objects for [['pebbles'], ['barney', 'fred']]

// The `_.matchesProperty` iteratee shorthand.
_.partition(users, ['active', false]);
// → objects for [['barney', 'pebbles'], ['fred']]

// The `_.property` iteratee shorthand.
_.partition(users, 'active');
// → objects for [['fred'], ['barney', 'pebbles']]

or ramda.partition

R.partition(R.contains('s'), ['sss', 'ttt', 'foo', 'bars']);
// => [ [ 'sss', 'bars' ],  [ 'ttt', 'foo' ] ]

R.partition(R.contains('s'), { a: 'sss', b: 'ttt', foo: 'bars' });
// => [ { a: 'sss', foo: 'bars' }, { b: 'ttt' }  ]