14-1 Recap of Key Concepts
Key Concepts
- Two-Way Data Binding
- Directives
- Controllers
- Services and Factories
- Dependency Injection
- Modules
- Filters
- Routing
- Promises
- Custom Directives
- Testing
- Performance Optimization
- Security
- Internationalization
1. Two-Way Data Binding
Two-way data binding in AngularJS allows for automatic synchronization of data between the model and the view. Changes in the model are reflected in the view, and vice versa.
Example:
<input ng-model="name" />
<p>Hello, {{name}}!</p>
Imagine two-way data binding as a mirror. When you change your appearance (model), the mirror (view) reflects the change instantly.
2. Directives
Directives are markers on a DOM element that tell AngularJS to attach a specified behavior to that element or even transform the DOM element and its children.
Example:
<div ng-show="isVisible">This content is visible.</div>
Think of directives as special instructions for your HTML. They tell the HTML elements (DOM) what to do and how to behave.
3. Controllers
Controllers in AngularJS are JavaScript functions that are bound to a particular scope. They are responsible for setting up the initial state and adding behavior to the scope.
Example:
app.controller('MyController', function($scope) {
$scope.message = 'Hello, World!';
});
Consider controllers as the brain of a robot. They control (manage) the behavior and actions of the robot (application).
4. Services and Factories
Services and factories in AngularJS are used to create reusable business logic. They provide a way to share data and functions across different parts of the application.
Example:
app.factory('myFactory', function() {
return {
getData: function() {
return 'Data from Factory';
}
};
});
Think of services and factories as toolboxes. Each toolbox (service/factory) contains tools (functions) that can be used in different projects (controllers).
5. Dependency Injection
Dependency Injection (DI) in AngularJS is a design pattern that allows you to inject dependencies into your components. It promotes modularity and testability.
Example:
app.controller('MyController', function($scope, myService) {
$scope.data = myService.getData();
});
Consider DI as a chef assembling a dish. The chef (controller) uses ingredients (services) provided by the kitchen (DI container) to prepare the meal (application).
6. Modules
Modules in AngularJS are used to organize the application into cohesive blocks of functionality. Each module can depend on other modules, allowing for modular development.
Example:
var app = angular.module('myApp', []);
Think of modules as chapters in a book. Each chapter (module) can stand alone but contributes to the overall story (application).
7. Filters
Filters in AngularJS are used to format the value of an expression for display to the user. They can be used in view templates, controllers, or services.
Example:
<p>{{ amount | currency }}</p>
Consider filters as magic wands. Each wand (filter) can transform data (input) into a desired form (output) with a simple wave.
8. Routing
Routing in AngularJS allows you to create single-page applications (SPAs) with multiple views. The ngRoute module provides routing and deeplinking services.
Example:
app.config(function($routeProvider) {
$routeProvider
.when('/home', {
templateUrl: 'home.html',
controller: 'HomeController'
})
.otherwise({
redirectTo: '/home'
});
});
Imagine routing as a tour guide. The guide (ngRoute) takes you (user) to different locations (views) within the same city (SPA) based on your request (URL).
9. Promises
Promises in AngularJS are used to handle asynchronous operations. They provide a way to manage the flow of asynchronous code.
Example:
app.controller('MyController', function($scope, $http, $q) {
var promise = $http.get('/api/data');
promise.then(function(response) {
$scope.data = response.data;
});
});
Think of promises as a guarantee from your messenger (HTTP request) that they will deliver the reply (response) as soon as possible, with a follow-up action based on the result.
10. Custom Directives
Custom directives in AngularJS allow you to create reusable HTML components. They extend HTML by adding new attributes or elements.
Example:
app.directive('myDirective', function() {
return {
restrict: 'E',
template: '<div>Custom Directive</div>'
};
});
Imagine custom directives as LEGO blocks. Each block (directive) can be used to build complex structures (web pages) in a modular way.
11. Testing
Testing in AngularJS involves writing unit tests with Jasmine and running them with Karma. This ensures your application is robust and free of bugs.
Example:
describe('Calculator', function() {
it('should add two numbers', function() {
expect(add(1, 2)).toBe(3);
});
});
Consider testing as quality control in a factory. Each product (component) is rigorously tested (unit tested) to ensure it meets the required standards (expected behavior).
12. Performance Optimization
Performance optimization in AngularJS involves techniques like lazy loading, minification, and caching to improve the speed and efficiency of your application.
Example:
app.config(function($routeProvider) {
$routeProvider
.when('/home', {
templateUrl: 'home.html',
controller: 'HomeController',
resolve: {
load: function($q, $timeout) {
var deferred = $q.defer();
$timeout(function() {
deferred.resolve();
}, 1000);
return deferred.promise;
}
}
});
});
Think of performance optimization as tuning a car. Each adjustment (technique) improves the performance (speed and efficiency) of the vehicle (application).
13. Security
Security in AngularJS involves protecting your application from common vulnerabilities like XSS, CSRF, and injection attacks.
Example:
app.config(function($httpProvider) {
$httpProvider.defaults.headers.common['X-Requested-With'] = 'XMLHttpRequest';
});
Consider security best practices as armor for your application. Each piece of armor (practice) protects against specific threats (vulnerabilities).
14. Internationalization
Internationalization in AngularJS allows you to create multilingual applications. The ngLocale module provides support for different locales and languages.
Example:
app.config(function($translateProvider) {
$translateProvider.translations('en', {
'HELLO': 'Hello'
});
$translateProvider.translations('es', {
'HELLO': 'Hola'
});
$translateProvider.preferredLanguage('en');
});
Think of internationalization as a translator. The translator (i18n) ensures that your application speaks (displays content) in the user's language.