Book Image

JavaScript from Beginner to Professional

By : Laurence Lars Svekis, Maaike van Putten, Codestars By Rob Percival
4 (5)
Book Image

JavaScript from Beginner to Professional

4 (5)
By: Laurence Lars Svekis, Maaike van Putten, Codestars By Rob Percival

Overview of this book

This book demonstrates the capabilities of JavaScript for web application development by combining theoretical learning with code exercises and fun projects that you can challenge yourself with. The guiding principle of the book is to show how straightforward JavaScript techniques can be used to make web apps ranging from dynamic websites to simple browser-based games. JavaScript from Beginner to Professional focuses on key programming concepts and Document Object Model manipulations that are used to solve common problems in professional web applications. These include data validation, manipulating the appearance of web pages, working with asynchronous and concurrent code. The book uses project-based learning to provide context for the theoretical components in a series of code examples that can be used as modules of an application, such as input validators, games, and simple animations. This will be supplemented with a brief crash course on HTML and CSS to illustrate how JavaScript components fit into a complete web application. As you learn the concepts, you can try them in your own editor or browser console to get a solid understanding of how they work and what they do. By the end of this JavaScript book, you will feel confident writing core JavaScript code and be equipped to progress to more advanced libraries, frameworks, and environments such as React, Angular, and Node.js.
Table of Contents (19 chapters)
16
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17
Index

Debugging

Debugging is a delicate art. In the beginning, it usually is very hard to spot what's wrong with your code. If you are using JavaScript in the browser and it is not behaving as you would expect, step 1 is always to open the console in the browser. Often it will contain errors that can help you further.

If that doesn't solve it, you can log to the console in every step of your code, and also log the variables. This will give you some insight as to what is going on. It might just be that you are relying on a certain variable that happens to be undefined. Or perhaps you are expecting a certain value from a mathematical computation, but you've made an error and the result is something completely different from what you thought. Using console.log() during development to see what's happening is rather common.

Breakpoints

A more professional way to go about debugging is to use breakpoints. This can be done from most browsers and IDEs. You click on...