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What is an AngularJS Module?
An AngularJS module is a container that holds different components like controllers, services, directives, and filters. It’s similar to how we organize Java classes into packages, except in AngularJS, it bundles together functionalities to build a web application.
Java Comparison:
Think of an AngularJS module as being similar to a package in Java, where you organize related classes. In Java, we use packages to structure our code for better organization and reuse. In AngularJS, a module groups various components like controllers, services, etc., and helps you structure your app.
Java Example:
// Java package declaration
package com.myapp;
public class MyController {
public String getMessage() {
return "Hello from Java!";
}
}
AngularJS Equivalent:
// AngularJS module declaration
var app = angular.module("myApp", []);
app.controller("myCtrl", function($scope) {
$scope.message = "Hello from AngularJS!";
});
AngularJS Module Syntax
The basic syntax to define an AngularJS module is:
var app = angular.module("myApp", [dependencies]);
Where myApp is the name of the module and [dependencies] is an array of other modules this module depends on. For example, ngRoute can be a dependency for routing in AngularJS.
Structure of an AngularJS Module
Just like how we use various classes like Controller, Service, etc., in Java, AngularJS modules contain components like controllers, directives, services, factories, and more.
angular.module("myApp", [dependencies])
.controller("myCtrl", function($scope) {})
.directive("myDirective", function() {})
.factory("myFactory", function() {})
.service("myService", function() {})
.filter("myFilter", function() {})
.constant("myConstant", value)
.value("myValue", value)
.config(function() {});
Each component has its specific role, just like a class in Java.
Example of a Simple AngularJS Module
Let’s look at a basic example of an AngularJS module that organizes different functionalities, much like how a Java package organizes classes.
<!DOCTYPE html>
<html ng-app="myApp">
<head>
<meta charset="UTF-8">
<title>AngularJS Module Example</title>
<script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.8.2/angular.min.js"></script>
</head>
<body>
<div ng-controller="myCtrl">
<h1>{{message}}</h1>
<p>{{myFactory.getMessage()}}</p>
<p>{{myService.getMessage()}}</p>
<p>{{"myValue: " + myValue}}</p>
<p>{{"myConstant: " + myConstant}}</p>
<p>{{"2 + 2 = " + (2 | myFilter)}}</p>
<my-directive></my-directive>
</div>
<script>
var app = angular.module("myApp", []);
// Controller
app.controller("myCtrl", function($scope, myFactory, myService, myValue, myConstant) {
$scope.message = "Welcome to AngularJS Module Example!";
$scope.myValue = myValue;
$scope.myConstant = myConstant;
});
// Directive
app.directive("myDirective", function() {
return {
template: "<p>This is myDirective!</p>"
};
});
// Factory
app.factory("myFactory", function() {
return {
getMessage: function() {
return "This is myFactory!";
}
};
});
// Service
app.service("myService", function() {
this.getMessage = function() {
return "This is myService!";
};
});
// Filter
app.filter("myFilter", function() {
return function(input) {
return input + 2;
};
});
// Constant
app.constant("myConstant", "I am a constant!");
// Value
app.value("myValue", "I am a value!");
// Config (can be used to configure routes, etc.)
app.config(function() {
// Configuration code here
});
</script>
</body>
</html>
Explanation:
- Controller: Similar to a
Servletin Java that handles requests and sends a response. - Directive: Allows you to create reusable components like custom HTML tags.
- Factory & Service: Both are similar to Java
ServiceorDAOclasses where you define logic for data handling. - Filter: Functions that process data before it’s shown in the view, like
Servletfilters. - Constant & Value: Static values that can be injected into your components, just like static constants in Java classes.
Adding Dependencies (like ngRoute)
You can include AngularJS modules as dependencies, similar to how you’d add libraries in Java.
Java Example (Adding Dependency):
// In Java, we add libraries using imports
import java.util.ArrayList;
AngularJS Example (Adding ngRoute):
var app = angular.module("myApp", ["ngRoute"]);
app.config(function($routeProvider) {
$routeProvider
.when("/home", {
template: "<h1>Welcome Home!</h1>"
})
.otherwise({
template: "<h1>Page not found</h1>"
});
});
In this example, the ngRoute module is added to handle client-side routing, just like Servlets handle routing in Java web applications.
Conclusion
AngularJS modules help you structure your application, just like packages in Java. By grouping controllers, services, directives, and other components, you can keep your code organized and maintainable.
Key Takeaways:
- AngularJS Module = Java Package.
- It organizes components like Controllers (similar to
Servlets), Factories/Services (similar to JavaServices), and Directives (similar to reusable UI components). - You can add dependencies to your module, just like importing Java libraries.
Now, you’re ready to create AngularJS modules and start organizing your code!