Two-way data binding is a feature in AngularJS that allows automatic synchronization of data between the model and the view. This means that when the data in the model changes, the view is automatically updated to reflect the new data, and vice versa.
In AngularJS, data is bound to the view through directives, which are special HTML attributes that define the behavior of the element they are attached to. Two-way data binding is implemented through the ng-model directive, which binds the value of an input field to a property on the model. When the user types something into the input field, the model is automatically updated with the new value, and when the model changes, the input field is automatically updated to reflect the new value.
For example, consider an input field that allows a user to enter their name. In AngularJS, you could use the ng-model directive to bind the input value to a property on the model, like this:
input type="text" ng-model="name"
Then, in your controller, you could define the "name" property on the model:
app.controller('myController', function($scope) {
$scope.name = 'John';
});
Now, when the page loads, the input field will be automatically populated with the value "John", and if the user changes the value, the "name" property on the model will be updated to reflect the new value.
Two-way data binding can make it easier to build complex, interactive user interfaces, but it can also have performance implications, especially when working with large data sets. Developers should be mindful of the potential impact on performance and consider using one-way data binding or other optimization techniques when appropriate.