Shorten an array or collection with an array of fields - backbone.js

Question

Scenario:
you have an array,
you have an array of some ids (eg: [1,3]),
you want to get a shortened array.
I cannot find how to do so if not in the lengthy way:
_.filter(... function (id) { return id==1 || id==3 })
Question: does such someMethod1 exist in underscore.js?
var frdsArr =
[
{id: 1, name: 'moe', age: 40},
{id: 2, name: 'larry', age: 50},
{id: 3, name: 'curly', age: 60}
];
var goodFrdsArr = _.someMethod1( frdsArr, 'id', [1, 3] );
/*
goodFrdsArr is [
{id: 1, name: 'moe', age: 40},
{id: 3, name: 'curly', age: 60}
];
*/
The same question with backbone.js: what about someMethod2?
var Friend = Backbone.Model.extend({});
var FriendsCollection = Backbone.Collection.extend({
model: Friend
});
var friendsCollection = new FriendsCollection( frdsArr );
var goodFriendsCollection = friendsCollection.someMethod2( 'id', [1,3] );
/*
goodFriendsCollection contains 2 instances of Friend Models
*/

Answer 1

Once you have found a suitable function, you can extend Underscore with _.mixin to simplify later calls. For example, you could create _.restrict to match your _.someMethod1 signature:
_.mixin({
// filter a list on an attribute having to match a list of values
// _.indexOf accepts an optional isSorted argument so let's pass it
restrict: function(list, attr, values, isSorted) {
return _.filter(list, function(obj) {
return _.indexOf(values, obj[attr], isSorted) !== -1;
});
}
});
var goodFrdsArr = _.restrict(frdsArr, 'id', [1, 3]);
See http://jsfiddle.net/nikoshr/cf0qs5gh/ for a demo
With this setup, you can modify Backbone.Collection's prototype to give all your collections this new capacity (more or less taken from the Backbone source code):
Backbone.Collection.prototype.restrict = function() {
var args = [].slice.call(arguments);
args.unshift(this.models);
return _.restrict.apply(_, args);
};
var friendsCollection = new Backbone.Collection(frdsArr);
var goodfriends = c.restrict('id', [1, 3]); //an array with 2 models
http://jsfiddle.net/nikoshr/cf0qs5gh/1/

Answer 2

var frdsArr =
[
{id: 1, name: 'moe', age: 40},
{id: 2, name: 'larry', age: 50},
{id: 3, name: 'curly', age: 60}
];
var filteredIDs = [1,3];
var filteredFrnds = _.filter(frdsArr, function(frnd){
return _.contains(filteredIDs, frnd.id);
})
console.log(filteredFrnds);
Make use of filter and contains
FIDDLE