How to use controllers in Angular

by gayathrimohan Updated: Jan 4, 2024

Guide Kit

AngularJS is a JS-based open-source front-end web application framework developed by Google. Users use it to simplify and streamline the process of building dynamics.

Single-page web apps do it. It provides a structured framework for organizing and developing client-side code. This makes it easier to create interactive and responsive web applications.

In AngularJS, it plays a crucial role in managing an application's data and behavior. They act as intermediaries among the view and the model. The MVC architecture uses it to ease the separation of concerns.

Data Binding: Controllers enable two-way data binding between the model and the view. Changes within inside the version replace the view, and vice versa.
Scope Management: Controllers define a scope. The scope stores variables. The template allows users to access and manipulate data within the scope.
Business Logic: Controllers contain the business logic of the application. They handle user interactions and process data. It is also used to coordinate with services to update the model.
Dependency Injection: Controllers use Dependency Injection to access various services.
Event Handling: Controllers manage events triggered by user actions.
Reusable Components: Controllers support the creation of reusable components.

AngularJS uses it to handle the application logic and interact with the view.

Here are the main types of controllers:

Regular controllers: Regular controllers associate specific views. The controller function defines those views. Developers use these with directives like ng-controller in HTML. The controller uses it to establish a connection with the view.
Route Controllers: Route Controllers associate specific routes in an AngularJS application. When configuring the route using $routeProvider, you define them.
Nested Controllers: AngularJS allows the nesting of controllers within controllers. This is useful for dividing complex functionality into smaller, manageable units. Each nested controller has its scope. It can inherit properties from its parent scope.

The controller function defines a controller in AngularJS.

The basic syntax looks like this:

angular.module('app'). controller ('MyController', function () {

// Controller logic and variables go here

});

with the "controller as" syntax:

You can bind the controller's properties and methods to a variable. This makes it more readable and avoids scope-related issues.

Some tips for creating efficient and reusable controllers:

Single Responsibility Principle (SRP)
Dependency Injection
Lean Controllers
Avoid Hard-Coding
Use Interfaces
Separation of Concerns
Error Handling
Versioning
Documentation
Unit Testing

In larger AngularJS applications, organizing controllers is crucial for maintainability.

Consider the following best practices:

Modularization
Folder Structure
Controller Naming
Single Responsibility
Use of Services
Hierarchy and Inheritance
Avoid Global Controllers
Route-based Organization
Documentation
Testing Considerations

In conclusion, developers use AngularJS controllers in dynamic and interactive web applications. They act because of the bridge between the version and the view. The system uses it to handle user interactions and update the model. Controllers encapsulate the application logic, promoting modular and maintainable code. Through two-way data binding, they enable real-time updates, enhancing the user experience. AngularJS controllers empower developers to create scalable, organized, and responsive web applications. Managing the application's behavior and user interactions accomplishes this.

Fig: Preview of the output that you will get on running this code from your IDE.

Code

AngularJS creating a controller

JavaScriptLines of Code : 35License : Strong Copyleft (CC BY-SA 4.0)

    <li data-ng-repeat="cust in customers | filter:name | orderBy: 'name'">
    {{cust.name}}:{{cust.city}}
    </li>

var demoApp = angular.module('demoApp', []);

demoApp.controller('SimpleController', function($scope) {
  $scope.customers = [{
      name: 'John Doe',
      city: 'new york'
    },
    {
      name: 'john smith',
      city: 'phoenix'
    },
    {
      name: 'jane doe',
      city: 'san francisco'
    }
  ];
});
<script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.2.23/angular.min.js"></script>
<div ng-app="demoApp" class="container" data-ng-controller="SimpleController">

  Name:
  <br />
  <input type="text" data-ng-model="name" />
  <br />
  <ul>
    <li data-ng-repeat="cust in customers | filter:name | orderBy: 'name'">
    {{cust.name}}:{{cust.city}}
    </li>
  </ul>

</div>

Instructions

Follow the steps carefully to get the output easily.

Install Visual Studio Code IDE on your computer.
Create a new HTML file.
Copy the code using the 'Copy' button and create an HTML tag then paste the code inside the tag into that HTML file.
Remove first three lines of code(no:1 to 3) and then create <html>tag.
Create a <script> tag inside the <body> tag Then keep the function (no:5to21)lines of codes inside the script tag(refer to preview as well).
<script> tag should be added below the <div> tag in <body> tag.
Save and run the HTML file directly from the file location to generate the output.

I hope you found this useful.

I found this code snippet by searching for 'How to use controllers in Angular ' you can try any such use case!

Environment Tested

I tested this solution in the following versions. Be mindful of changes when working with other versions.

The solution is created and tested in Visual Studio Code 1.85.1.

Using this solution, we are able to use controllers in Angular with simple steps. This process also facilities an easy way to use, hassle-free method to create a hands-on working version of code which would help us to use controllers in Angular.

FAQ

1. What is the purpose of an AngularJS controller in an application?

An application uses it to handle business logic. The model and the view use it to manage the flow of data and respond to user actions. It helps organize and structure the code by separating concerns.

2. How does the ng-controller directive work with AngularJS controllers?

A controller associated with a particular section of the HTML. It tells AngularJS which controller to use for a specific part of the DOM. It allows the controller to interact with and manipulate that part of the view.

3. Can you explain the structure and functionality of a controller object in AngularJS?

In AngularJS, you define a controller as a JavaScript function. You can create it using the controller method, and it requires a name and a function as parameters. The function includes the logic and properties that define the controller's behavior. Scope is often used to interact with the view.

4. How can we use nested controllers in an AngularJS Sample Application?

People use it to create a hierarchical structure for managing different parts of an app. Child controllers can inherit properties and methods from their parent controllers. This allows for better organization of code. Also allows for the separation of concerns in larger applications.

5. What role does a JS file play in creating and managing AngularJS controllers?

A JS file in AngularJS often contains the definition of controllers. The angular.module method creates controllers. The associated controller uses it to define its name and function. To recognize and use the defined controllers include JS file in the application.

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