Coding is a life time learning task. Start develop app or webpage after learning the fundamentals. Continue to learn new and advance technic regardless of the need for current product or not, because new version is replacing old one as time passes. Fundamentals is the start point for every new product. Any new color is still composed from the red green and blue or any new word is still composed from the 26 letters.

Webpage, Database and App are interrelated. Knowledge of webpage and database will help to build a better IOS and Android app that needs resource from server.

HTML

Builds webpages with tags, style with CSS or JavaScript. Declare <!DOCTYPE>. Create the root element with language attribute <html lang="en"></html> that contents a <head></head> element and a <body></body> element.

Page title, metadata descriptions, external files, style ...etc. are inside <head></head>.

Inside <body></body>, all visible and invisible contents are create here. Additional inline style is described inside element tag right after the beginning tagname. JavaScript can be added with the <script></script>tag or call function from external file that is loaded with src attribute inside the <script></script>tag.

CSS

Style webpage layout, inline, internal and external.

Inline Style is used to style the local element and it will replace any previous style.

Internal Style sheet is created with <style></style> tag and placed inside <head></head>. It is good for multible elements in the same webpage.

External style sheet is a file that contains webpage style and load with the <link rel="stylesheet" href="filename.css" ></link> tag. It is good for the style that use in multible webpages.

JavaScript

JavaScript is client side script. It can do every thing for a webpage. Beside the interactive contents, it can also create HTML and CSS style.

Current page menu is created with JavaScript, so it can load the menu according to browser device and window size.

JavaScript can make game that play in browser. I will try this in my coming leisure time.

MySQL

fundamental Knowledge. Need more practice and experience.

PHP

fundamental Knowledge. Need more practice and experience.

Swift

Swift is Apple's modern programming language. It can build almost every thing. Use SceneKit to make 3D game and SpriteKit is for 2D game. Use SwiftUI instead of Storyboard make better and less coding for app.

Swift Playgrounds is a good place to test an individual code before put it into the project.

Swift package is in learing.

Java

fundamental Knowledge. Need more practice and experience.