The output returned by an AngularJS controller

John Papa introduced the 'controller as' technique for AngularJS in his article titled Do You Like Your Angular Controllers with or without Sugar:

myApp.controller("MainCtrl", [
    function () {
        var vm = this;  // using ViewModel convention
        vm.person = { name: "Bob" };
        return vm;
    }]);
  

What is the significance of the return vm; line in the code provided? Does it serve any specific purpose considering that the code works perfectly fine even without it?

Answer №1

When Angular creates your controller, it will utilize the new keyword on the function you provided. This results in the construction of a new object using the constructor you passed in. Returning objects from your constructor function will prompt Angular to use that specific instance of your newly created object, similar to how JavaScript constructors are typically used.

There are some nuances to keep in mind during the construction process (refer to this SO answer for more details):

  1. If the returned object is the same as this, it can be omitted since this will be utilized by default.
  2. In cases where a primitive type or null is returned (essentially anything that is not an Object), this will also be used.
  3. Returning an instance will result in the reference to that specific instance being returned.

It should be noted that stating this will be utilized in points 1 & 2 is an oversimplification. For more specific information, please refer to this detailed explanation regarding construction.

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