Array partition based on 'contain'

Question

var array = [ "123-foo", "456-bar", "789-baz" ];
var selected = [ "123", "789" ];

var partition_contains = _.partition(array, function(value){
    return _.contains(selected, value);
});
console.log(partition_contains);

var partition_filter = _.partition(array, function(value){
    return !!_.filter(selected, function(s){ return value.indexOf(s) !== -1; }).length;
});
console.log(partition_filter);

<script src="https://cdnjs.cloudflare.com/ajax/libs/underscore.js/1.9.1/underscore-min.js"></script>

The output is:

[
  [],
  [
    "123-foo",
    "456-bar",
    "789-baz"
  ]
]

Expected output:

[
  [
    "123-foo",
    "789-baz"
  ],
  [
    "456-bar"
  ]
]

Why doesn't contain work as I expect although internally its using indexOf?

Edit: Works with filter but wonder why not contains?

Answer 1

From first approach, I think it is because _.contains match exact value between array and the targeted value.

console.log(_.contains(selected, "123-foo")); // false

My solution will use some method from Array.

var partitioned = _.partition(array, value => selected.some(select => value.indexOf(select) > -1));
console.log(partitioned);

I saw underscore.js also has _.some method.