10 Apache Cordova Interview Questions and Answers

Apache Cordova is a popular open-source mobile development framework that allows developers to build cross-platform mobile applications using HTML, CSS, and JavaScript. By leveraging web technologies, Cordova enables the creation of apps that can run on multiple platforms, such as iOS, Android, and Windows, without the need for native coding. This makes it an attractive choice for developers looking to maximize their reach while minimizing development time and effort.

This article offers a curated selection of interview questions designed to test your knowledge and proficiency with Apache Cordova. Reviewing these questions will help you solidify your understanding of the framework and prepare you to confidently discuss your skills and experience in a technical interview setting.

Apache Cordova Interview Questions and Answers

1. Explain the architecture of a Cordova application.

Apache Cordova is a mobile application development framework that allows developers to build applications using HTML, CSS, and JavaScript. The architecture of a Cordova application includes several components:

• WebView: This is the core component that renders the HTML, CSS, and JavaScript code within a native application container.
• Plugins: These are essential for accessing native device features like the camera and GPS, acting as a bridge between the WebView and native code.
• Config.xml: This file defines the application’s metadata, including its name, version, and permissions.
• Platform-specific code: Sometimes necessary for custom functionality not covered by existing plugins.
• HTML, CSS, and JavaScript: The front-end code responsible for the user interface and application logic.

2. What are Cordova plugins and how do you install them? Provide an example.

Cordova plugins allow a Cordova application to access native device features not available through standard web APIs. They provide a JavaScript interface for the app to interact with.

To install a plugin, use the Cordova CLI:

cordova plugin add <plugin-name>

For example, to install the Camera plugin:

cordova plugin add cordova-plugin-camera

Here’s how to use the Camera plugin to take a photo:

document.getElementById("takePhoto").addEventListener("click", function() {
    navigator.camera.getPicture(onSuccess, onFail, { 
        quality: 50,
        destinationType: Camera.DestinationType.DATA_URL
    });

    function onSuccess(imageData) {
        var image = document.getElementById('myImage');
        image.src = "data:image/jpeg;base64," + imageData;
    }

    function onFail(message) {
        alert('Failed because: ' + message);
    }
});

3. Write a code snippet to access the device’s camera using a Cordova plugin.

To access the device’s camera using Cordova, use the Camera Plugin. First, install it:

cordova plugin add cordova-plugin-camera

Then, use this code snippet:

document.getElementById("cameraButton").addEventListener("click", function() {
    navigator.camera.getPicture(onSuccess, onFail, { 
        quality: 50,
        destinationType: Camera.DestinationType.DATA_URL
    });

    function onSuccess(imageData) {
        var image = document.getElementById('myImage');
        image.src = "data:image/jpeg;base64," + imageData;
    }

    function onFail(message) {
        alert('Failed because: ' + message);
    }
});

4. What are some common security concerns in Cordova applications and how do you mitigate them?

Common security concerns in Cordova applications include:

• Insecure Data Storage: Storing sensitive data without encryption can lead to breaches.
• Untrusted Content: Loading content from untrusted sources can expose the app to XSS attacks.
• Insecure Communication: Transmitting data over unsecured channels can lead to man-in-the-middle attacks.
• Code Injection: Allowing untrusted input to be executed as code can lead to injection attacks.
• Improper Use of Plugins: Using unvetted plugins can introduce vulnerabilities.

To mitigate these concerns:

• Encrypt Sensitive Data: Use strong encryption algorithms.
• Content Security Policy (CSP): Implement a strict CSP.
• Secure Communication: Use HTTPS for data transmission.
• Input Validation: Validate and sanitize all user inputs.
• Vetting Plugins: Use trusted and well-maintained plugins.

5. Explain how to use Cordova’s File API to read and write files.

Cordova’s File API allows developers to read and write files on a device’s file system. To use it, include the cordova-plugin-file in your project.

Example:

document.addEventListener('deviceready', function() {
    window.resolveLocalFileSystemURL(cordova.file.dataDirectory, function(directoryEntry) {
        directoryEntry.getFile('example.txt', { create: true, exclusive: false }, function(fileEntry) {
            // Write to the file
            fileEntry.createWriter(function(fileWriter) {
                fileWriter.onwriteend = function() {
                    console.log('Write completed.');
                };
                fileWriter.onerror = function(e) {
                    console.log('Write failed: ' + e.toString());
                };
                var dataObj = new Blob(['Hello, world!'], { type: 'text/plain' });
                fileWriter.write(dataObj);
            });

            // Read from the file
            fileEntry.file(function(file) {
                var reader = new FileReader();
                reader.onloadend = function() {
                    console.log('File content: ' + this.result);
                };
                reader.readAsText(file);
            }, function(error) {
                console.log('Error reading file: ' + error.code);
            });
        }, function(error) {
            console.log('Error creating file: ' + error.code);
        });
    }, function(error) {
        console.log('Error accessing file system: ' + error.code);
    });
});

6. How do you implement push notifications in a Cordova application?

To implement push notifications in a Cordova application, use a plugin like “phonegap-plugin-push”. This plugin allows you to receive notifications on Android and iOS devices.

Example:

• Install the plugin:

  cordova plugin add phonegap-plugin-push
  

• Initialize the plugin:

  document.addEventListener('deviceready', function () {
      var push = PushNotification.init({
          android: {},
          ios: {
              alert: "true",
              badge: "true",
              sound: "true"
          }
      });
  
      push.on('registration', function (data) {
          console.log('Registration ID:', data.registrationId);
          // Send the registration ID to your server
      });
  
      push.on('notification', function (data) {
          console.log('Notification received:', data.message);
          // Handle the notification
      });
  
      push.on('error', function (e) {
          console.error('Error with push notifications:', e.message);
      });
  }, false);
  

7. How do you handle errors in a Cordova application? Provide a code example.

Error handling in a Cordova application involves using standard JavaScript techniques like try-catch blocks and leveraging Cordova-specific error events.

Example:

document.addEventListener('deviceready', function() {
    try {
        navigator.camera.getPicture(onSuccess, onError, { quality: 50, destinationType: Camera.DestinationType.DATA_URL });

        function onSuccess(imageData) {
            var image = document.getElementById('myImage');
            image.src = "data:image/jpeg;base64," + imageData;
        }

        function onError(message) {
            console.error('Camera failed: ' + message);
            alert('Failed because: ' + message);
        }
    } catch (e) {
        console.error('An unexpected error occurred: ' + e.message);
        alert('An unexpected error occurred: ' + e.message);
    }
}, false);

8. Describe how to use Cordova’s InAppBrowser plugin. Provide a code example.

The InAppBrowser plugin in Cordova is used to open URLs in a new browser instance within the app. This is useful for displaying web content without leaving the app context.

To use the InAppBrowser plugin, install it:

cordova plugin add cordova-plugin-inappbrowser

Use the cordova.InAppBrowser.open method to open a URL:

document.addEventListener('deviceready', function() {
    var url = 'https://www.example.com';
    var target = '_blank';
    var options = 'location=yes';

    var ref = cordova.InAppBrowser.open(url, target, options);

    ref.addEventListener('loadstart', function() {
        console.log('Loading started: ' + event.url);
    });

    ref.addEventListener('loadstop', function() {
        console.log('Loading finished: ' + event.url);
    });

    ref.addEventListener('exit', function() {
        console.log('Browser is closed');
    });
}, false);

9. How do you debug a Cordova application on an Android device?

To debug a Cordova application on an Android device, use tools like Chrome DevTools and the Android Debug Bridge (ADB).

• Chrome DevTools: Inspect and debug the web content of your Cordova application.
• Android Debug Bridge (ADB): A command-line tool to communicate with an Android device.

To start debugging:

1. Connect your Android device to your computer via USB and enable USB debugging.
2. Open a terminal and navigate to your Cordova project’s root directory.
3. Use the following command to build and run your application:

      cordova run android --device
   ```</li>
   <li>Open Chrome and navigate to `chrome://inspect`. You should see your device listed under "Remote Target."</li>
   <li>Click "Inspect" next to your application's entry to open Chrome DevTools.</li>
   </ol>
   
   <h4>10. Write a code snippet to store data locally using Cordova's storage API.</h4>
   
   Cordova provides a simple API for storing data locally using the `window.localStorage` object. This data persists even after the app is closed and reopened.
   
   Example:
   
   ```javascript
   // Store data
   window.localStorage.setItem("username", "JohnDoe");
   
   // Retrieve data
   var username = window.localStorage.getItem("username");
   console.log(username); // Outputs: JohnDoe