Detailed explanation of the use of custom directives in AngularJS

Detailed explanation of the use of custom directives in AngularJS_AngularJS

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Release： 2016-05-16 15:54:28

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Use AngularJS to extend the functionality of HTML in custom instructions. Functional definition of the "command" used by the custom directive. The custom directive simply replaces the element it is activated on. During the bootstrapping process the AngularJS application finds the matching element and prepares an activity using the custom directive's compile() method before processing the element using the directive's scope-based custom directive's link() method. AngularJS provides support for creating custom directives based on the following element types.

Element directives - Directives that activate a matching element when encountered.
Attribute - - Activates a matching attribute when the directive is encountered.
CSS - - Activate matching CSS styles when the directive is encountered.
Comment - - Activates the matching comment when the command is encountered.

Learn about custom directives

Define custom HTML tags.

<student name="Mahesh"></student><br/>
<student name="Piyush"></student>

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Define custom directives to handle the custom HTML tags above.

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;
});

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Define a controller to update the scope as a directive. Here, we use the name attribute value as the scope of the 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;
});

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Example

<html>
<head>
  <title>Angular JS Custom Directives</title>
</head>
<body>
  <h2>AngularJS Sample Application</h2>
  <div ng-app="mainApp" ng-controller="StudentController">
 <student name="Mahesh"></student><br/>
 <student name="Piyush"></student>
  </div>
  <script src="http://ajax.googleapis.com/ajax/libs/angularjs/1.2.15/angular.min.js"></script>
  <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>

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Results

Open textAngularJS.html in your web browser. See the results as follows:

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