# Meaningful Comments: The Art of Adding Value with Words

When it comes to code, clarity is king. While well-written code should be self-explanatory, sometimes a nudge in the right form of a comment can make all the difference. However, not all comments are created equal, and there's a fine line between enlightening and excessive.

### Why Comment?

1. **Clarification**: Even the cleanest code can have complex logic or algorithms that need some context. A well-placed comment can provide that insight.
2. **Documentation**: For API developers or library creators, comments are often transformed into user-facing documentation.
3. **Intent**: What is this code trying to achieve? While the 'what' is evident from the code, the 'why' often isn't.
4. **TODOs and FIXMEs**: Pointing out where improvements can be made or bugs need addressing.

### Characteristics of Meaningful Comments

* **Relevant**: Only comment when necessary. Superfluous comments can clutter the code.
* **Concise**: Get to the point quickly. A novel in the comments can be a distraction.
* **Timely**: Comment while writing or refactoring. A fresh perspective ensures accuracy.
* **Maintainable**: Outdated comments can mislead. Ensure they evolve with the code.

### The Case Against Comments

1. **Self-documenting Code**: The belief that clean, descriptive variable and function names can replace the need for comments.
2. **Maintenance Overhead**: Comments can become outdated, leading to confusion.
3. **Redundancy**: Comments that just restate the obvious can be deemed noise.
4. **Agile Practices**: With continuous iteration, the code can change frequently, making comments a moving target.

### Striking the Balance

* Prioritise readability and understanding.
* Value the time of the person who will eventually read or maintain the code (which might be future you!).
* Respect the agreed-upon team practices and guidelines.

### Examples of Meaningful Comments

#### 1. Explaining Complex Logic

Without Comment:

```javascript
function calculateDiscount(price, user) {
    return price * (1 - (user.memberSince / 100));
}
```

With Comment:

```javascript
// Calculates a discount based on how long the user has been a member.
// For each year of membership, the user gets a 1% discount.
function calculateDiscount(price, user) {
    return price * (1 - (user.memberSince / 100));
}
```

Refactored with Naming Conventions:

```javascript
function calculateMembershipBasedDiscount(price, user) {
    const annualDiscountPercentage = user.yearsAsMember / 100;
    return price * (1 - annualDiscountPercentage);
}
```

#### 2. Describing Intent

Without Comment:

```javascript
const threshold = 100;
if (user.points > threshold) {
    unlockFeature(user);
}
```

With Comment:

```javascript
// Unlock a premium feature for users who've amassed more than a set threshold of points
const threshold = 100;
if (user.points > threshold) {
    unlockFeature(user);
}
```

Refactored with Naming Conventions:

```javascript
const premiumFeaturePointsThreshold = 100;
if (user.points > premiumFeaturePointsThreshold) {
    unlockPremiumFeature(user);
}
```

#### TODOs and FIXMEs

```javascript
function processPayment(user) {
    // TODO: Implement a fraud detection mechanism
    // FIXME: Payment sometimes fails with currency conversion issues
    return initiatePayment(user.cart);
}
```

#### Explaining a Workaround

Original:

```python
def fetch_data():
    // Using a try-except block due to intermittent API failures.
    // This is a temporary solution until the API is stabilized.
    try:
        return api_request()
    except APIError:
        return backup_request()
}
```

Refactored with Naming Conventions:

```python
def fetch_data_with_backup():
    try:
        return primary_api_request()
    except APIError:
        return backup_api_request()
}
```

### Examples of Redundant or Bad Comments

#### Stating the Obvious

```javascript
// Setting variable x to 10
let x = 10;
```

#### Outdated Comment

```javascript
// Uses v1.0 of the API (Note: The API is now on v2.5)
fetchDataFromAPI();
```

#### Ambiguous Comment

```javascript
// Fix this
calculateTax(income);
```

## Takeaways

* Aim for clarity in code first, then use comments to fill in the gaps.
* Make each comment count; ensure it adds value.
* Stay adaptive. The best approach is one that serves the team and the project's evolving needs.

## Exercises & Examples

1. Review a section of your code. Remove any redundant comments and add ones that clarify intent.
2. In a team meeting, discuss the team's stance on comments. Can improvements be made in current practices?
