Ralph's Blog about this and that (RSS | Atom)

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A look at Angular's ngFor directive

Published: 22. January 2017  •  Updated: 5. December 2017  •  angular, javascript

Consume Protocol Buffer messages with Ionic

Published: 14. January 2017  •  Updated: 1. December 2018  •  ionic, spring, java, javascript

Form validation with Angular and Spring Boot

Published: 26. January 2017  •  Updated: 4. December 2018  •  angular, ionic, spring, java, javascript

Example of form validation in an Ionic application. How to create custom synchronous and asynchronous validators and how to validate data on the server with the Java Bean Validation framework.

JavaScript Date and moment.js

Published: 4. January 2017  •  Updated: 25. October 2017  •  javascript

Storing data with localStorage and Lockr

Published: 20. January 2017  •  Updated: 19. June 2017  •  database, javascript

Integrate ECharts into an Ionic app

Published: 22. February 2017  •  Updated: 29. September 2018  •  ionic, javascript

In this post, we look at a way to display charts from the ECharts library in an Ionic app

JWT Authentication with Ionic/Angular and Spring Boot

Published: 5. February 2017  •  Updated: 7. December 2018  •  ionic, spring, java, javascript

How to implement a JWT authentication system with Ionic/Angular and Spring Boot.

Lovefield, a SQL database engine for the web

Published: 27. February 2017  •  Updated: 29. November 2018  •  database, ionic, javascript

A short introduction to Lovefield, a JavaScript SQL database engine. And how to build an Ionic app that uses Lovefield as database access layer.

Sending push messages from Spring Boot to Ionic over FCM

Published: 26. February 2017  •  Updated: 31. March 2020  •  ionic, spring, javascript, java

This post describes how a Spring Boot can send messages over FCM to an Ionic / Cordova app

Uploading files from Ionic / Cordova to Minio / S3

Published: 16. February 2017  •  Updated: 6. December 2018  •  ionic, cordova, spring, s3, javascript, java

How to upload files from an Ionic / Cordova app directly to a Minio server or Amazon S3 with pre-signed URLs.

Uploading pictures from Ionic / Cordova to Spring Boot

Published: 12. February 2017  •  Updated: 6. December 2018  •  ionic, cordova, spring, javascript, java

In this article, we create an Ionic application where the user can take a picture, and the app uploads it to a Spring Boot application.

A closer look at IndexedDB

Published: 12. September 2017  •  Updated: 30. October 2017  •  database, javascript

IndexedDB, the database in the browser. How does it work and what can you do with it.

A closer look at the Web Cryptography API

Published: 25. September 2017  •  Updated: 4. December 2018  •  javascript, cryptography, ionic

Creating a trivial password manager with the Web Cryptography API and the Ionic framework.

Offline capable Ionic Web App with IndexedDB

Published: 15. September 2017  •  Updated: 3. December 2018  •  database, javascript, ionic

Example of an Ionic web application that stores data in an IndexedDB and works offline.

Spring Boot and Ionic application development with OpenAPI

Published: 21. September 2017  •  Updated: 4. December 2018  •  spring, java, javascript, ionic

In this blog, we create REST services in Spring Boot and consume them in an Ionic app. We use the OpenAPI specification for generating API documentation and the client TypeScript code.

Upload files from Ionic to Spring Boot with Flow.js

Published: 26. September 2017  •  Updated: 4. December 2018  •  java, ionic, javascript, spring

A closer look at the Flow.js JavaScript library that helps upload files from a browser to the server. Flow.js is a JavaScript library providing multiple simultaneous, stable, fault-tolerant, and resumable/restartable file uploads via the HTML5 File API.

Developing a self-hosted location tracker

Published: 7. November 2017  •  Updated: 5. December 2018  •  ionic, java, spring, javascript

In this blog post, we create a self-hosted location tracker that consists of three parts. An Ionic/Cordova application that continuously sends the current location to a Spring Boot application from where the locations are broadcasted to a website and visualized on Google Maps.

Dynamically loading position data with Ionic and Spring Boot

Published: 5. November 2017  •  Updated: 3. December 2018  •  ionic, java, spring, javascript

In this blog post we create an Ionic app that dynamically requests location data points from a Spring Boot server and displays them on an OpenStreetMap map. The data points are stored in a MongoDB database, and we take advantage of the geospatial query support to read the data points only for a certain area.

Adding speech recognition to an Ionic App

Published: 18. December 2017  •  Updated: 16. July 2019  •  ionic, javascript, java, spring

In this blog post I present three different way how to integrate a speech recognition functionality into an Ionic app. With a Cordova plugin, the Web Speech API and with RecordRTC and the Google Cloud Speech API.

A closer look at date-fns

Published: 8. January 2018  •  Updated: 22. August 2019  •  javascript

A closer look at the date-fns date/time library. Compare it with Moment.js and look at a few examples.

A closer look at the Cache API

Published: 9. January 2018  •  pwa, javascript

Explore the provided methods of the Cache API that is primarily used in Service Workers to cache assets, but can be used anywhere as a general-purpose cache.

Custom SVG icons with Ionic

Published: 6. January 2018  •  Updated: 1. December 2018  •  ionic, ionic, javascript

How to use arbitrary SVG icons in Ionic

IndexedDB programming with Dexie.js

Published: 12. January 2018  •  database, javascript

In this blog post, I give you an overview of Dexie, a minimalistic wrapper library for IndexedDB. Write simpler and more concise IndexedDB code with Dexie.

Integrate Parcel into a Maven project

Published: 13. January 2018  •  Updated: 31. October 2021  •  java, javascript

An example project that integrates a front end JavaScript application with the Parcel bundler and a Spring Boot application built with Maven into one project and ultimately create one executable JAR.

Self-host Polyfill.io

Published: 15. January 2018  •  Updated: 2. February 2023  •  javascript, selfhost

A short tutorial on how to self-host Polyfill.io on Ubuntu

Sending Web push messages from Spring Boot to Browsers

Published: 9. January 2018  •  Updated: 7. December 2018  •  java, javascript, pwa, spring

In this blog post I show you how you can send push messages from a Spring Boot application over Firebase Cloud Messaging (FCM) to connected clients with the Web Push API. The Push API is part of the Service Worker specification and does not depend on any native plugins.

Using Dexie.js in a TypeScript application

Published: 12. January 2018  •  Updated: 3. December 2018  •  database, javascript, ionic

In this blog post I present a way to use Dexie in a TypeScript application

Conditionally load polyfills

Published: 14. February 2018  •  javascript

Two examples of how you can conditionally load polyfills in a JavaScript application

Human readable regular expressions

Published: 27. February 2018  •  java, javascript

Writing human readable regular expressions with the VerbalExpression library

Real-Time Polling App with Java and JavaScript

Published: 28. February 2018  •  Updated: 31. October 2021  •  java, javascript

In this blog post, we create a simple polling application with Java and JavaScript and send real-time updates with server-sent events

Check for commonly used or compromised passwords

Published: 3. May 2018  •  java, javascript

In this blog post, I present four examples of how you can implement password checks for commonly used or compromised passwords.

A closer look at the Background Sync API

Published: 26. June 2018  •  pwa, javascript, java, spring, ionic

This blog post takes a closer look at the Background Sync API, part of the service worker implementation, and presents an example that uses Background Sync to synchronize data between an Ionic web application and a Spring Boot server application.

Angular project with Workbox service worker

Published: 22. June 2018  •  Updated: 30. March 2020  •  pwa, javascript

This tutorial describes how to integrate a service worker written with the Workbox library, into an Angular application

A closer look at the Beacon API

Published: 5. September 2018  •  javascript

The Beacon API in the browser can be used to transfer data to a server. Its primary use case is to send analytics data during the unload event of a web page. In this blog post, we're going to look at the API and create some examples that use the Beacon API to send data to a server.

BigInt, arbitrary precision integers in JavaScript

Published: 3. September 2018  •  javascript

A closer look at the ES2020 numeric primitive BigInt

Global error handler in Angular

Published: 5. October 2018  •  javascript

How to install a global error handler in an Angular application and send error reports to a back end. The blog post shows you how to collect error reports while the application is offline and send them to a back end as soon as the device is back online.

Text to speech with Google Cloud Text-to-Speech

Published: 4. October 2018  •  java, javascript

Converting text from a web application into speech with Google Cloud Text-to-Speech

Using the Background Sync API with the Angular service worker

Published: 9. December 2018  •  pwa, javascript, ionic

In this blog post, we look at a way to use the Background Sync API together with Angular's service worker. Or, in general, how to add custom service worker code to a generated Angular service worker.

Google Cloud Vision and Storage example with Ionic and Spring Boot

Published: 11. December 2018  •  java, spring, ionic, javascript

This blog post shows you a way to upload pictures from a web application to Google Cloud Storage and run them through Google Cloud Vision. The application uses Ionic for the front end and Spring Boot for the back end. It utilizes signed URLs for permitting the client to upload pictures directly from the web application to Google Cloud Storage

Building a simple neural network with Java and JavaScript

Published: 23. December 2018  •  java, javascript

Creating a simple feedforward neural network in Java and JavaScript, based on the algorithms of Tariq Rashid's book "Make Your Own Neural Network"

Real-time messaging with Cettia and Spring Boot

Published: 28. January 2019  •  java, javascript, spring

Getting started with Cettia, a real-time web framework, and Spring Boot

JavaScript BigInt and JSON

Published: 4. January 2019  •  javascript, java

How to JSON deserialize and serialize the new JavaScript primitive number type BigInt in a full-stack application with Spring Boot

Machine Learning with brain.js and Tensorflow.js

Published: 4. January 2019  •  javascript

In this blog post we are going to create two neural networks with brain.js and Tensorflow.js, train the MNIST dataset and use the trained model in a web application to detect digits

Using pre-trained Tensorflow.js models

Published: 4. January 2019  •  javascript

In this blog post we are going to look at tfjs-models (https://github.com/tensorflow/tfjs-models), a collection of pre-trained models with Tensorflow.js that you can simply add and use from your web application

JavaScript spread and rest syntax examples

Published: 19. January 2019  •  javascript

A collection of examples with the spread and rest syntax in JavaScript

Integrate FontAwesome icons in an Angular application

Published: 15. February 2019  •  Updated: 21. August 2019  •  javascript, ionic

This blog post shows you how to integrate FontAwesome icons into an Angular application with the official Angular JavaScript library

Password auto-login with the Credential Management API

Published: 13. June 2019  •  java, javascript, spring, ionic

How to create a frictionless password auto-login experience with the Credential Management API.

Exposing build information of Spring Boot and Angular applications

Published: 12. June 2019  •  java, spring, javascript

How to expose build information, like version number, build timestamp, git commit information, of Spring Boot and Angular applications

Google Fonts in an Angular / Ionic application

Published: 10. June 2019  •  javascript, ionic

A tutorial on how to use Google Fonts in an Angular / Ionic app. The blog post presents two approaches. One approach is by linking to the Google Font server, and the second approach shows you how to download Google Fonts and serve them from your web server.

Reliable file uploads over HTTP with tus.io

Published: 11. June 2019  •  java, javascript, spring, ionic

How to integrate tus.io implementations into JavaScript and Java applications to create reliable and resumable file uploads over HTTP.

Uploading pictures from Capacitor app to Spring Boot

Published: 11. June 2019  •  java, spring, javascript, ionic, capacitor

How to take pictures with the Capacitor camera plugin and upload them to a Spring Boot application with Angular's HttpClient and tus.io.

OCR in the browser with Tesseract.js

Published: 30. July 2019  •  Updated: 30. December 2019  •  javascript

In this blog post, we will develop an Angular/Ionic application that runs Optical character recognition (OCR) in a browser with Tesseract.js. This application does not depend on any server-side code, and the recognition process runs locally in the browser.

A look at the Page Visibility API

Published: 29. July 2019  •  javascript

What is the Page Visibility API and how can you access it in web applications. Also, a quick look at the visibilityjs library that simplifies commons tasks with the Page Visibility API.

Web Workers - Basic usage, Angular and Comlink

Published: 31. July 2019  •  javascript

In this blog post, we are looking at the Web Workers API. What problem it solves, and how can we use it in our JavaScript applications. We take a look at the Angular build-time support for Web Workers, and lastly, we take a look at Comlink, a JavaScript library that simplifies Web Workers programming.

ky - elegant fetch

Published: 10. August 2019  •  javascript

A closer look at ky, a JavaScript HTTP client for the browser, built on top of the Fetch API. ky adds convenient functions and new features to the Fetch API.

Creating a password-less sign-in with WebAuthn, Spring, and Ionic/Angular

Published: 25. August 2019  •  javascript, java, spring, ionic

In this blog post, we will build a password-less authentication system with the FIDO2 WebAuthn standard. I will show you a full-stack demo application with an Ionic / Angular front end and a Spring Boot back end with Spring Security.

Sending Web Push Notifications with Java

Published: 13. August 2019  •  java, javascript

Sending Web Push notifications from a Java back end to a web browser

Translation chat app with Cettia and Google Cloud Translation

Published: 24. April 2020  •  Updated: 20. May 2021  •  javascript, spring, java

In this blog post, I show you how to build a chat application with Cettia and Google Cloud Translation that automatically translates chat messages.

Push Notifications with Capacitor and Java

Published: 3. April 2020  •  Updated: 20. June 2021  •  ionic, spring, javascript, capacitor, java

In this blog post we take a closer look at how to receive push notifications with Capacitor and how to send them from a Spring Boot application

JavaScript / Java chat application with Cettia

Published: 23. April 2020  •  Updated: 20. May 2021  •  javascript, spring, java

In this blog post, I show you how to build a simple chat application with a JavaScript front- and a Java backend.

Exchange Protocol Buffers messages between JavaScript and Java

Published: 4. April 2020  •  Updated: 20. May 2021  •  javascript, java

In this blog post, we are going to take a look at how to sends Protocol Buffers messages from an Angular app to a Spring Boot back end.

YouTube Player and Google Maps Angular component

Published: 21. April 2020  •  Updated: 21. May 2021  •  javascript, angular

In this blog post, we take a look at the YouTube Player and Google Maps component from the angular/component repository.

RxJS webSocket, w3c-compatible WebSocket wrapper

Published: 11. April 2020  •  Updated: 20. May 2021  •  javascript

In this blog post, we take a closer look at the webSocket function from the RxJS library, a wrapper around the native WebSocket object.

Building encrypted chat app with the Web Cryptography API

Published: 3. May 2020  •  Updated: 20. May 2021  •  javascript, spring, java, ionic

In this blog post, I show you how to create an encrypted Java/JavaScript chat application with the Web Cryptography API.

Present photos on Google Maps

Published: 2. May 2020  •  Updated: 31. October 2021  •  javascript, java

In this tutorial, I show you how to develop a web application that presents your holiday photos on Google Maps

Add CAPTCHA to your site with hCaptcha

Published: 1. May 2020  •  Updated: 20. May 2021  •  javascript, java, ionic, angular

This blog post shows you how to integrate hCaptcha CAPTCHAs into a plain JavaScript project and Angular projects, with a Spring Boot back end.

Getting started with Nebular for Angular

Published: 17. May 2020  •  javascript, angular

How to create an Angular application from scratch with the Nebular component library.

Dexie.js live queries

Published: 22. January 2022  •  javascript, database, ionic

In this blog post, I will show you an example of the new live query feature in Dexie.js 3.2 that enables an application to subscribe to IndexedDB queries.