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How to add comments in JavaScript

Let's Unravel the Mystery of Comments in JavaScript

Learning a new programming language can sometimes feel like learning to speak an entirely new language. However, just like spoken languages, programming languages also have ways to express thoughts, share ideas, and communicate with others. In this case, we're talking about comments in JavaScript.

The Concept of Comments

Imagine you're writing a letter to a friend. In this letter, you decide to make some notes for yourself about what you've written. These notes could include reminders, explanations, or even jokes. You wouldn't want your friend to read these notes, so you write them in a way that only you can understand.

In the world of programming, these personal notes are called 'comments'. Comments are lines of code that are ignored by the computer but can be read by humans. They are used to explain what the code does, remind ourselves and inform others about something important in the code.

Writing Your First Comment

In JavaScript, there are two types of comments, single-line comments, and multi-line comments. Let's start with single-line comments.

A single-line comment starts with two forward slashes //. Here's an example:

// This is a single-line comment in JavaScript

This line of code won't affect your program at all. It's like a whisper in a loud room - the computer can't hear it, but other programmers can.

Next, we have multi-line comments. These comments can span multiple lines and are enclosed between /* and */.

This is a multi-line comment.
You can write as many lines as you want.
The computer will ignore all of them.

The Art of Commenting

Now that we know how to write comments, let's talk about when and how to use them effectively.

Keep It Simple and Clear

Comments should be easy to understand. Think of it as explaining your code to a five-year-old. The clearer your explanation, the easier it is for others (and future you) to understand your code.

Don't State the Obvious

Comments should provide useful information. If your code is self-explanatory, it doesn't need a comment. For example, this is unnecessary:

// increase x by 1

The code itself already clearly expresses that x is being increased by 1. A comment here is redundant and adds no new information.

Explain Why, Not What

A good comment explains why something is done, not what is being done. The code shows what is happening, but it may not be clear why it's happening. For example:

// Due to performance concerns, we use a for loop instead of forEach here
for(let i = 0; i < array.length; i++) { ... }

This comment informs us why a certain decision was made in the code, which is not immediately apparent from the code itself.

The Power of Comments

Comments are not just for clarification. They also have the power to temporarily disable parts of your code. This is known as 'commenting out'.

Let's say you have a function that's causing errors and you want to isolate the problem. You can 'comment out' this function to see how your program works without it. Here's how you can do it:

function problematicFunction() {
  // some problematic code here

By commenting out, the function problematicFunction will be ignored, like it doesn't exist in the eyes of the computer.

Wrapping Up

Comments are like the secret notes passed around in a classroom. They're not part of the official lesson (your program), but they can help you (and others) understand what's going on.

Just as too many notes can make it hard to focus on the actual lesson, over-commenting can make your code hard to read. Comment wisely, comment effectively, and your code will be as understandable as a well-written book.

In the end, remember that you're not just coding for a machine, but also for humans. Machines may understand your code no matter how complex it is, but humans need a bit more help. That's where comments come in, bridging the gap between human understanding and machine language. So, go ahead, leave a note, make a joke, provide an explanation. Your future self, and anyone else who reads your code, will thank you.