I'm currently learning AngularJS and am having difficulty understanding the difference between ng-bind
and ng-model
.
Can anyone tell me how they differ and when one should be used over the other?
ng-bind has one-way data binding ($scope --> view). It has a shortcut {{ val }}
which displays the scope value $scope.val
inserted into html where val
is a variable name.
ng-model is intended to be put inside of form elements and has two-way data binding ($scope --> view and view --> $scope) e.g. <input ng-model="val"/>
.
tosh's answer gets to the heart of the question nicely. Here's some additional information....
Filters & Formatters
ng-bind
and ng-model
both have the concept of transforming data before outputting it for the user. To that end, ng-bind
uses filters, while ng-model
uses formatters.
filter (ng-bind)
With ng-bind
, you can use a filter to transform your data. For example,
<div ng-bind="mystring | uppercase"></div>
,
or more simply:
<div>{{mystring | uppercase}}</div>
Note that uppercase
is a built-in angular filter, although you can also build your own filter.
formatter (ng-model)
To create an ng-model formatter, you create a directive that does require: 'ngModel'
, which allows that directive to gain access to ngModel's controller
. For example:
app.directive('myModelFormatter', function() {
return {
require: 'ngModel',
link: function(scope, element, attrs, controller) {
controller.$formatters.push(function(value) {
return value.toUpperCase();
});
}
}
}
Then in your partial:
<input ngModel="mystring" my-model-formatter />
This is essentially the ng-model
equivalent of what the uppercase
filter is doing in the ng-bind
example above.
Parsers
Now, what if you plan to allow the user to change the value of mystring
? ng-bind
only has one way binding, from model-->view. However, ng-model
can bind from view-->model which means that you may allow the user to change the model's data, and using a parser you can format the user's data in a streamlined manner. Here's what that looks like:
app.directive('myModelFormatter', function() {
return {
require: 'ngModel',
link: function(scope, element, attrs, controller) {
controller.$parsers.push(function(value) {
return value.toLowerCase();
});
}
}
}
Play with a live plunker of the ng-model
formatter/parser examples
What Else?
ng-model
also has built-in validation. Simply modify your $parsers
or $formatters
function to call ngModel's controller.$setValidity(validationErrorKey, isValid)
function.
Angular 1.3 has a new $validators array which you can use for validation instead of $parsers
or $formatters
.
Angular 1.3 also has getter/setter support for ngModel
ngModel
This directive executes at priority level 1.
Example Plunker
JAVASCRIPT
angular.module('inputExample', [])
.controller('ExampleController', ['$scope', function($scope) {
$scope.val = '1';
}]);
CSS
.my-input {
-webkit-transition:all linear 0.5s;
transition:all linear 0.5s;
background: transparent;
}
.my-input.ng-invalid {
color:white;
background: red;
}
HTML
<p id="inputDescription">
Update input to see transitions when valid/invalid.
Integer is a valid value.
</p>
<form name="testForm" ng-controller="ExampleController">
<input ng-model="val" ng-pattern="/^\d+$/" name="anim" class="my-input"
aria-describedby="inputDescription" />
</form>
ngModel is responsible for:
Binding the view into the model, which other directives such as input, textarea or select require.
Providing validation behavior (i.e. required, number, email, url).
Keeping the state of the control (valid/invalid, dirty/pristine, touched/untouched, validation errors).
Setting related css classes on the element (ng-valid, ng-invalid, ng-dirty, ng-pristine, ng-touched, ng-untouched) including animations.
Registering the control with its parent form.
ngBind
This directive executes at priority level 0.
Example Plunker
JAVASCRIPT
angular.module('bindExample', [])
.controller('ExampleController', ['$scope', function($scope) {
$scope.name = 'Whirled';
}]);
HTML
<div ng-controller="ExampleController">
<label>Enter name: <input type="text" ng-model="name"></label><br>
Hello <span ng-bind="name"></span>!
</div>
ngBind is responsible for:
Replacing the text content of the specified HTML element with the value of a given expression.
If you are hesitating between using ng-bind
or ng-model
, try to answer these questions:
Do you only need to display data?
Yes: ng-bind (one-way binding)
No: ng-model (two-way binding)
Do you need to bind text content (and not value)?
Yes: ng-bind
No: ng-model (you should not use ng-bind where value is required)
Is your tag a HTML ?
Yes: ng-model (you cannot use ng-bind with tag)
No: ng-bind
ng-model
ng-model directive in AngularJS is one of the greatest strength to bind the variables used in application with input components. This works as two way data binding. If you want to understand better about the two way bindings, you have an input component and the value updated into that field must be reflected in other part of the application. The better solution is to bind a variable to that field and output that variable whereever you wish to display the updated value throughoput the application.
ng-bind
ng-bind works much different than ng-model. ng-bind is one way data binding used for displaying the value inside html component as inner HTML. This directive can not be used for binding with the variable but only with the HTML elements content. Infact this can be used along with ng-model to bind the component to HTML elements. This directive is very useful for updating the blocks like div, span, etc. with inner HTML content.
This example would help you to understand.
angular.module('testApp',[]).controller('testCTRL',function($scope) { $scope.testingModel = "This is ModelData.If you change textbox data it will reflected here..because model is two way binding reflected in both."; $scope.testingBind = "This is BindData.You can't change this beacause it is binded with html..In above textBox i tried to use bind, but it is not working because it is one way binding."; }); div input{ width:600px; }
Diff b/w model and bind{{testingModel}}
ngModel usually use for input tags for bind a variable that we can change variable from controller and html page but ngBind use for display a variable in html page and we can change variable just from controller and html just show variable.
We can use ng-bind with <p>
to display, we can use shortcut for ng-bind {{model}}
, we cannot use ng-bind with html input controls, but we can use shortcut for ng-bind {{model}}
with html input controls.
<input type="text" ng-model="name" placeholder="Enter Something"/>
<input type="text" value="{{name}}" placeholder="Enter Something"/>
Hello {{name}}
<p ng-bind="name"</p>
Success story sharing