Talking about Angularjs two-way binding

Three important ways to bind two-way:

• $scope. $apply ()
• $scope. $digest ()
• $scope. $watch ()

I. $scope. $watch ()

$watch function is to add a listener to the $scope, and when the listening data changes, the listener will receive a prompt and perform certain actions. When you specify the following two functions for $watch, you can create a listener:

• An expression that specifies the part of the data that you are interested in, such as "User.firstname".
• A listener function that is used to accept prompts when data changes.

In order to implement $watch, we need to store listener objects. Add an array on the scope constructor:

function Scope () {  this. $ $watchers = [];} 

$$ in angular that this variable is considered private and should not be called in external code.

Talking about Angularjs two-way binding