About the author:

All posts by Terence:

Fixing the e.indexOf is not a function error

Fixing the “e.indexOf is not a function” error on your website

If you have a WordPress site that was built before August 2020 (when WordPress 5.5 decided to stop supporting jQuery Migrate), or if you manage a site that recently weaned off jQuery Migrate, you might run into errors where the parts of your site that run on Javascript stop working.

When you open the Developer tools of your browser (that’s the F12 key for most browsers), you might also see an error message that looks something like this.

Uncaught TypeError: e.indexOf is not a function
    at S.fn.load (jquery.min.js?ver=3.6.0:2:84932)
    at headings.min.js?ver=3.19.4:1:2579
    at headings.min.js?ver=3.19.4:1:2706
Continue reading
Why is calling setters in Java constructors discouraged?

Why is calling setters from constructors discouraged in Java?

In Java, coders are discouraged from calling setter functions in class constructors. Even though doing so can sometimes reduce the amount of repeated code.

Consider the following class:

Unit.java

public class Unit {
	protected int health;

	public Unit(int hp) {
		// Prevents health for being set to 0 or less.
		if(hp <= 0)
			throw new IllegalArgumentException("Health must be more than 0.");
		health = hp;
	}

	public void setHealth(int hp) {
		// Prevents health for being set to 0 or less.
		// Repeat of the code in the constructor.
		if(hp <= 0)
			throw new IllegalArgumentException("Health must be more than 0.");

		health = hp;
	}

}

Instead of doing the check twice across 2 functions to ensure the incoming hp value is correct, it might occur to some coders that we can call the setter within the constructor instead, to reduce the amount of repeated code:

Unit.java

public class Unit {
	protected int health;

	public Unit(int hp) {
		// Prevents health for being set to 0 or less.
		if(hp <= 0)
			throw new IllegalArgumentException("Health must be more than 0.");
		health = hp;
		setHealth(hp);
	}

	public void setHealth(int hp) {
		// Prevents health for being set to 0 or less.
		// Repeat of the code in the constructor.
		if(hp <= 0)
			throw new IllegalArgumentException("Health must be more than 0.");

		health = hp;
	}
}

This, however, is discouraged, because (according to textbooks) setters like setHealth() can be overriden by child classes, creating unexpected or buggy behaviour in these child classes.

Continue reading
Java's Scanner.nextLine() is being skipped

Java’s Scanner nextLine() call is being skipped

As a programming language with its fair share of quirks, one of the many things a new Java programmer will run into is the issue of their Scanner.nextLine() calls being ignored. Consider the following Java code:

JavaNextLineProblem.java

import java.util.Scanner;
public class JavaNextLineProblem {
	public static void main(String[] args) {
		Scanner input = new Scanner(System.in);

		// Prompt the user to enter their name.
		System.out.print("Enter your name: ");
		String name = input.nextLine();

		// Prompt the user to enter their age.
		System.out.print("Enter your age: ");
		int age = input.nextInt();

		// Prompt the user to enter a description.
		System.out.print("Describe yourself in a sentence: ");
		String description = input.nextLine();

		// Prompt the user to enter a message.
		System.out.print("Enter a message: ");
		String message = input.nextLine();
	}
}

This is the desired result (user input coloured in green):

Enter your name: John
Enter your age: 21
Describe yourself in a sentence: I am awesome.
Enter a message: Hello world!

However, this is what you actually get:

Enter your name: John
Enter your age: 21
Describe yourself in a sentence: Enter a message: Hello world!

The program skips over the collection of input for the Describe yourself in a sentence prompt, and goes straight into collecting the input for the Enter a message prompt. What’s going on?

Continue reading
What to do when gitignore doesn't work

How to fix .gitignore not working on your repository

If you’re using a Git-based source control, you might be familiar with the use of a .gitignore file to list files which Git is supposed to ignore when tracking files and making commits. This can be particularly useful when using Git (if you’re using GitHub Desktop, you’re also using Git) as a source control tool for projects that generate temporary or user-specific files at every run, such as Unity, as these files cannot be shared across different users of the project.

User-generated files in Unity
User-generated files in Unity that don’t need to be tracked by Git.

Sometimes, when setting up the repository, because of a .gitignore that is not properly set up, files that you intend to be ignored can actually get committed into the repository. If that happens, retroactively applying the .gitignore list will not help.

Continue reading
A primer on Base 64 strings — Part 1

A primer on Base 64 strings — Part 1: Introduction

If you have been around the web for awhile, you will notice that sometimes, you will find a series of gibberish alphabets appearing, most often in your browser address bar as part of a website’s URL:

The blue highlighted portions in the GIF above are the aforementioned gibberish alphabets.

These are Base 64 characters, and a large portion of the web uses these characters for a multitude of purposes.

Continue reading
Finding which is the shorter 2D angle

Calculating the shorter angle of rotation in 2D

Here’s a really simple math problem in 2D games development that has a surprisingly complex solution. If I were to give you angles a and b, how would you calculate 1) the direction — that is, clockwise being positive; and anti-clockwise being negative — and 2) magnitude of the shorter angle of rotation from a to b?

Main angle question
We want the angle in green.

When you visualise it, both values seem so obvious; which was why I was so surprised I couldn’t figure it out. On the surface, it seems really simple — if you just take b – a, doesn’t it give you the solution?

Continue reading
Static variables explained, in Java

Static variables, explained (using Java)

One of the more complicated concepts that beginning programmers have trouble grasping is static variables. This is in part because static variables work in a way that is quite opposite to how classes and Object-Oriented Programming (OOP) work.

Since examples work wonders in explaining concepts, here’s a use-case in Java that will help to illustrate the concept. Don’t code in Java? No problem. OOP concepts are (mostly) the same across programming languages.

Continue reading