When using angular.copy, instead of updating the reference, a new object is created and assigned to the destination(if a destination is provided). But there's more. There's this cool thing that happens after a deep copy.
Say you have a factory service which has methods which updates factory variables.
angular.module('test').factory('TestService', [function () {
var o = {
shallow: [0,1], // initial value(for demonstration)
deep: [0,2] // initial value(for demonstration)
};
o.shallowCopy = function () {
o.shallow = [1,2,3]
}
o.deepCopy = function () {
angular.copy([4,5,6], o.deep);
}
return o;
}]);
and a controller which uses this service,
angular.module('test').controller('Ctrl', ['TestService', function (TestService) {
var shallow = TestService.shallow;
var deep = TestService.deep;
console.log('****Printing initial values');
console.log(shallow);
console.log(deep);
TestService.shallowCopy();
TestService.deepCopy();
console.log('****Printing values after service method execution');
console.log(shallow);
console.log(deep);
console.log('****Printing service variables directly');
console.log(TestService.shallow);
console.log(TestService.deep);
}]);
When the above program is run the output will be as follows,
****Printing initial values
[0,1]
[0,2]
****Printing values after service method execution
[0,1]
[4,5,6]
****Printing service variables directly
[1,2,3]
[4,5,6]
Thus the cool thing about using angular copy is that, the references of the destination are reflected with the change of values, without having to re-assign the values manually, again.