AngularJS lets you extend HTML with new attributes called Directives.
AngularJS has a set of built-in directives which offers functionality to your applications.
AngularJS also lets you define your own directives.
AngularJS Directives
AngularJS directives are extended HTML attributes with the prefix
ng-.
The
ng-app directive initializes an AngularJS application.
The
ng-init directive initializes application data.
The
ng-model directive binds the value of HTML controls (input, select, textarea) to application data.
Read about all AngularJS directives in our AngularJS directive reference.
Example
<div ng-app="" ng-init="firstName='John'">
<p>Name: <input type="text" ng-model="firstName"></p>
<p>You wrote: {{ firstName }}</p>
</div>
The
ng-app directive also tells AngularJS that the <div> element is the "owner" of the AngularJS application.Data Binding
The
{{ firstName }} expression, in the example above, is an AngularJS data binding expression.
Data binding in AngularJS binds AngularJS expressions with AngularJS data.
{{ firstName }} is bound with ng-model="firstName".
In the next example two text fields are bound together with two ng-model directives:
Example
<div ng-app="" ng-init="quantity=1;price=5">
Quantity: <input type="number" ng-model="quantity">
Costs: <input type="number" ng-model="price">
Total in dollar: {{ quantity * price }}
</div>
Using
ng-init is not very common. You will learn how to initialize data in the chapter about controllers.Repeating HTML Elements
The
ng-repeat directive repeats an HTML element:Example
<div ng-app="" ng-init="names=['Jani','Hege','Kai']">
<ul>
<li ng-repeat="x in names">
{{ x }}
</li>
</ul>
</div>
The
ng-repeat directive actually clones HTML elements once for each item in a collection.
The
ng-repeat directive used on an array of objects:Example
<div ng-app="" ng-init="names=[
{name:'Jani',country:'Norway'},
{name:'Hege',country:'Sweden'},
{name:'Kai',country:'Denmark'}]">
<ul>
<li ng-repeat="x in names">
{{ x.name + ', ' + x.country }}
</li>
</ul>
</div>
AngularJS is perfect for database CRUD (Create Read Update Delete) applications.
Just imagine if these objects were records from a database.
Just imagine if these objects were records from a database.
The ng-app Directive
The
ng-app directive defines the root element of an AngularJS application.
The
ng-app directive will auto-bootstrap (automatically initialize) the application when a web page is loaded.The ng-init Directive
The
ng-init directive defines initial values for an AngularJS application.
Normally, you will not use ng-init. You will use a controller or module instead.
You will learn more about controllers and modules later.
The ng-model Directive
The
ng-model directive binds the value of HTML controls (input, select, textarea) to application data.
The
ng-model directive can also:- Provide type validation for application data (number, email, required).
- Provide status for application data (invalid, dirty, touched, error).
- Provide CSS classes for HTML elements.
- Bind HTML elements to HTML forms.
Read more about the
ng-model directive in the next chapter.Create New Directives
In addition to all the built-in AngularJS directives, you can create your own directives.
New directives are created by using the
.directive function.
To invoke the new directive, make an HTML element with the same tag name as the new directive.
When naming a directive, you must use a camel case name,
w3TestDirective, but when invoking it, you must use -separated name, w3-test-directive:Example
<body ng-app="myApp">
<w3-test-directive></w3-test-directive>
<script>
var app = angular.module("myApp", []);
app.directive("w3TestDirective", function() {
return {
template : "<h1>Made by a directive!</h1>"
};
});</script>
</body>
You can invoke a directive by using:
- Element name
- Attribute
- Class
- Comment
The examples below will all produce the same result:
Element name
<w3-test-directive></w3-test-directive>
Attribute
<div w3-test-directive></div>
Class
<div class="w3-test-directive"></div>
Comment
<!-- directive: w3-test-directive -->
Restrictions
You can restrict your directives to only be invoked by some of the methods.
Example
By adding a
restrict property with the value "A", the directive can only be invoked by attributes:
var app = angular.module("myApp", []);
app.directive("w3TestDirective", function() {
return {
restrict : "A",
template : "<h1>Made by a directive!</h1>"
};
});
The legal restrict values are:
Efor Element nameAfor AttributeCfor ClassMfor Comment
By default the value is
EA, meaning that both Element names and attribute names can invoke the directive.
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