unless() : The unless() method will execute the given callback when the first argument given to the method evaluates to false:const collection = collect([1, 2, 3]);
collection.unless(false, items => items.push(4));
collection.all();
// [1, 2, 3, 4]unlessEmpty() : Alias for the whenNotEmpty() methodunlessNotEmpty() : Alias for the whenEmpty() method