Backbone.js过滤器集合返回一个对象，而不是一个集合

Question

I'm trying to filter a collection of models, but filter only seems to be returning an object and not a collection. From what I've read, wrapping the filter function in _() will force it to use underscore.js built in filter, and return the same type. But this doesn't seem to be working. Code is below, any thoughts?

    var clients = this.get('clients')

    if (clients instanceof Backbone.Collection) {
      console.log('clients is a collection');
    } else if (_.isObject(clients)) {
      console.log('clients is an object');
    } else if (_.isArray(clients)) {
      console.log('clients is an array');
    } else {
      console.log('clients is not known');
    }

    clients = _(clients.filter(function (client) {
      return client.get('case_studies').length;
    }));

    if (clients instanceof Backbone.Collection) {
      console.log('clients is a collection');
    } else if (_.isObject(clients)) {
      console.log('clients is an object');
    } else if (_.isArray(clients)) {
      console.log('clients is an array');
    } else {
      console.log('clients is not known');
    }

This is my output:

    clients is a collection
    clients is an object 

Answer 1

Assuming you instantiated your clients collection like this:

var Client = Backbone.Model.extend({});
var Clients = Backbone.Collection.extend({
  model: Client
});
var clients = new Clients();

Then all you'd need to do is:

clients = new Clients(clients.filter(function (client) {
  return client.get('case_studies').length
}));