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// 1. Single-line comment example
// The following code logs "Hello, World!" to the console.
console.log('Hello, World!'); // This message is displayed in the console.

// 2. Multi-line comment example
/*
The code below defines variables a and b,
and logs their sum to the console.
*/
let a = 10;
let b = 20;
console.log(a + b); // The result is 30.

// 3. Code explanation example
// Assign 100 to the variable c.
let c = 100;

// 4. Code disabling example
// The code below is commented out and won't execute.
//

// 5. TODO and FIXME notation example
// TODO: Implement the following function in the future.
function futureFunction() {
  // FIXME: This function is not yet complete.
}

// End of the comment examples that do not affect code execution.

# Comment

Comments are used by developers to explain the purpose, functionality, changes in the code, or to temporarily disable parts of the code.

 

## Types of JavaScript Comments

JavaScript uses different comment symbols for single-line and multi-line comments.

 

### Single-line Comment

A single-line comment begins with `//` and comments out the rest of the line.

```javascript title="Example of Comment Usage"
// This is a single-line comment
console.log('Hello, World!'); // This message will be printed to the console
```

 

### Multi-line Comment

A multi-line comment starts with `/*` and ends with `*/`. This style is used for comments that span multiple lines.

```javascript title="Multi-line Comment"
/*
This is a multi-line comment.
The content within the comment is not executed.
*/
console.log('Hello, World!');
```

 

## Usage of JavaScript Comments

1. Code Explanation: Use comments to describe the function, operation principles, or purpose of variables or functions in the code.

```javascript title="Explaining Code with Comments"
// Assign 10 to the variable x.
let x = 10;
```

 

2. Code Deactivation: Comments can be used to disable specific code parts temporarily for bug tracking, debugging, or other purposes.

```javascript title="Disabling Specific Code"
// console.log("This won't run");
```

 

3. Indicating TODO and FIXME: Adding comments to parts of the code that are under development or need modification allows you to easily find and fix them later. `TODO` is used to indicate tasks that need to be done, while `FIXME` highlights parts needing correction.

```javascript title="TODO Comment for Future Tasks"
// TODO: Implement additional features here
```

 

## Caution:

- Although comments do not affect code execution, excessive commenting can reduce code readability. It is best to use comments appropriately where necessary.

- Avoid including sensitive information or unnecessary personal details in comments.

In JavaScript, a single-line comment starts with `//` and extends to the end of that line. This is useful for developers to explain certain parts of the code or temporarily disable code.

### What is the most appropriate word to fill in the blank?