Custom directives are used in AngularJS to extend the functionality of HTML. Custom directives are defined using “directive” function. A custom directive simply replaces the element for which it is activated. AngularJS application during bootstrap finds the matching elements and do one time activity using its compile() method of the custom directive then process the element using link() method of the custom directive based on the scope of the directive. AngularJS provides support to create custom directives for following type of elements.

Element directives − Directive activates when a matching element is encountered.
Attribute − Directive activates when a matching attribute is encountered.
CSS − Directive activates when a matching css style is encountered.
Comment − Directive activates when a matching comment is encountered.

Understanding Custom Directive

Define custom html tags.

Define custom directive to handle above custom html tags.

var mainApp = angular.module(“mainApp”, []);

//Create a directive, first parameter is the html element to be attached.

//We are attaching student html tag.

//This directive will be activated as soon as any student element is encountered in html

mainApp.directive(‘student’, function() {

//define the directive object

var directive = {};

//restrict = E, signifies that directive is Element directive

directive.restrict = ‘E’;

//template replaces the complete element with its text.

directive.template = “Student: <b>{{student.name}}</b> ,

Roll No: <b>{{student.rollno}}</b>”;

//scope is used to distinguish each student element based on criteria.

directive.scope = {

student : “=name”

}

//compile is called during application initialization. AngularJS calls

it once when html page is loaded.

directive.compile = function(element, attributes) {

element.css(“border”, “1px solid #cccccc”);

//linkFunction is linked with each element with scope to get the element specific data.

var linkFunction = function($scope, element, attributes) {

element.html(“Student: <b>”+$scope.student.name +”</b> ,

Roll No: <b>”+$scope.student.rollno+”</b><br/>”);

element.css(“background-color”, “#ff00ff”);

}

return linkFunction;

}

return directive;

});

Define controller to update the scope for directive. Here we are using name attribute’s value as scope’s child.

mainApp.controller(‘StudentController’, function($scope) {

$scope.Mahesh = {};

$scope.Mahesh.name = “Mahesh Parashar”;

$scope.Mahesh.rollno = 1;

$scope.Piyush = {};

$scope.Piyush.name = “Piyush Parashar”;

$scope.Piyush.rollno = 2;

});

Example

<html>

<head>

<title>Angular JS Custom Directives</title>

</head>

<body>

<h2>AngularJS Sample Application</h2>

</div>

</script>

var mainApp = angular.module(“mainApp”, []);

mainApp.directive(‘student’, function() {

var directive = {};

directive.restrict = ‘E’;

directive.template = “Student: <b>{{student.name}}</b> ,

Roll No: <b>{{student.rollno}}</b>”;

directive.scope = {

student : “=name”

}

directive.compile = function(element, attributes) {

element.css(“border”, “1px solid #cccccc”);

var linkFunction = function($scope, element, attributes) {

element.html(“Student: <b>”+$scope.student.name +”</b> ,

Roll No: <b>”+$scope.student.rollno+”</b><br/>”);

element.css(“background-color”, “#ff00ff”);

}

return linkFunction;

}

return directive;

});

mainApp.controller(‘StudentController’, function($scope) {

$scope.Mahesh = {};

$scope.Mahesh.name = “Mahesh Parashar”;

$scope.Mahesh.rollno = 1;

$scope.Piyush = {};

$scope.Piyush.name = “Piyush Parashar”;

$scope.Piyush.rollno = 2;

});

</script>

</body>

</html>

Result

Open textAngularJS.htm in a web browser. See the result.

So, this brings us to the end of blog. This Tecklearn ‘Custom Directives in Angular JS’ blog helps you with commonly asked questions if you are looking out for a job in Angular JS and Front-End Development. If you wish to learn Angular JS and build a career in Front-End Development domain, then check out our interactive, Angular JS Training, that comes with 24*7 support to guide you throughout your learning period. Please find the link for course details:

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Introduction to Angular
Comparison between front-end tools
Angular Architecture
Building blocks of Angular
Angular Installation
Angular CLI
Angular CLI commands
Angular Modules

Angular Components and Data Binding

Working of Angular Applications
Angular App Bootstrapping
Angular Components
Creating A Component Through Angular CLI
Ways to specify selectors
Template and styles
Installing bootstrap to design application
Data Binding
Types of Data Binding
Component Interaction using @Input and @Output decorator
Angular Animations

TypeScript

What is TypeScript
Need of TypeScript
How to install TypeScript
Nodemon for monitoring changes
Interfaces in Class, String Templates, Maps,
Sets and Object Restructuring

Directives and Pipes in Angular

Angular Directives
@Component Directive
Structural Directives
Attribute Directives
Custom Directives
Pipes
Built-in Pipes
Chaining pipes
Custom pipes
Pipe Transform Interface & Transform Function
Pure and Impure pipes

Angular Services and Dependency Injection

Angular service
Need for a service
Dependency Injection
Creating a service
Hierarchical Injector
Injecting A Service into Another Service
Observables
RxJS Library
Angular’s Interaction with Backend
Parts of an Http Request
HttpClient

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Forms in Angular
What are their functions
Advantages of Forms
Various Types of Forms
What is Angular Validation and Model driven approach

Angular Routing

Angular Routing
Angular Routing benefits and features
Building a single page application and updating it dynamically with Angular Routing
What is Parameter Routing
Router Lifecycle Hooks and Child Routes

Authentication and Security in Angular

What is Authentication?
Authentication and authorization
Types of Authentication
Where to store tokens?
JSON Web Tokens (JWT)
Authentication in Angular application
Security threats in web application

Testing Angular applications

Testing of Angular applications
Deployment of Angular Test Bed for testing on Angular framework
Setup of various tools for testing
Testing services in Angular Framework
E2E and Document Object Model testing

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