Ember.makeArray()

Forces the passed object to be part of an array. If the object is already an array, it will return the object. Otherwise, it will add the object to an array. If obj is null or undefined, it will return an empty array.

Ember.makeArray();            // []
Ember.makeArray(null);        // []
Ember.makeArray(undefined);   // []
Ember.makeArray('lindsay');   // ['lindsay']
Ember.makeArray([1, 2, 42]);  // [1, 2, 42]

let controller = Ember.ArrayProxy.create({ content: [] });

Ember.makeArray(controller) === controller;  // true