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Code Comments - JavaScript Interview Questions

Code Quality: Comments in JavaScript

What are code comments in JavaScript?​

View Answer:
Interview Response: Coding comments are notes added to a program's source code to explain the code to programmers or to serve as reminders for future updates.

Code Example:

There are two types of comments in JavaScript:

Single line comments: These begin with two forward slashes //. Everything to the right of // on the same line is a comment.

// This is a single line comment in JavaScript

Multi-line comments: These begin with /* and end with */. Everything between /* and */ is a comment, even if it spans multiple lines.

/*
 This is a multi-line comment
 in JavaScript
*/

Remember, while comments are important for code readability and maintainability, they do not affect the execution of the code.

Why are coding comments important in JavaScript?​

View Answer:
Interview Response: Code comments in JavaScript serve to explain code, improve readability, and assist in debugging. They provide context and clarification, making it easier for developers to maintain and understand the codebase.

How do you reduce the number of unnecessary comments in your code?​

View Answer:
Interview Response: The key to reducing unnecessary comments in your code is to write self-descriptive code. The best way to achieve this is to replace a chunk of code with a function.

Code Example: Confusing Code

function showPrimes(n) {
  nextPrime: for (let i = 2; i < n; i++) {
    // check if i is a prime number   <-- this is an unnecessary comment
    for (let j = 2; j < i; j++) {
      if (i % j == 0) continue nextPrime;
    }

    console.log(i);
  }
}

Code Example: Good Code

// The better variant, with a factored-out function isPrime:
function showPrimes(n) {
  for (let i = 2; i < n; i++) {
    if (!isPrime(i)) continue;

    console.log(i);
  }
}

function isPrime(n) {
  for (let i = 2; i < n; i++) {
    if (n % i == 0) return false;
  }

  return true;
}

What are Good comments in JavaScript?​

View Answer:
Interview Response: Good comments in JavaScript provide a high-level overview of the code architecture, including how components interact. They focus less on explaining code functionality and more on documenting function parameters and usage. They provide a bird's eye view of the code.

Code Example:

/**
 * Returns x raised to the n-th power.
 *
 * @param {number} x The number to raise.
 * @param {number} n The power, must be a natural number.
 * @return {number} x raised to the n-th power.
 */
function pow(x, n) {
  ...
}

How can you document function parameters in JavaScript comments?​

View Answer:
Interview Response: You use the param tag followed by the name and description of the parameter. For example, "param {string} name - the name of the person."

Code Example:

/**
 * @param {number} a - The first number
 * @param {number} b - The second number
 */
function add(a, b) {...}

What is the purpose of JSDoc comments?​

View Answer:
Interview Response: JSDoc comments in JavaScript are used to document code. They provide descriptions of functions, parameters, return values, and more, improving readability and aiding in generating documentation automatically.

Code Example:

/**
 * Calculates the sum of two numbers.
 *
 * @param {number} a - The first input number
 * @param {number} b - The second input number
 * @returns {number} The sum of a and b
 */
function sum(a, b) {
  return a + b;
}

How do you document code using JSDoc comments?​

View Answer:
Interview Response: To document code using JSDoc, start with /**, describe elements using tags like @param, @return, @class, and @type, add descriptions, and close with */. This allows for automatic documentation generation and IDE support.

How do you write a single-line comment in JavaScript?​

View Answer:
Interview Response: We use two forward slashes (//) followed by the comment text to write a single-line comment in JavaScript.

How do you write a multi-line comment in JavaScript?​

View Answer:
Interview Response: To create a multi-line comment in JavaScript, place your comment between a forward slash followed by an asterisk (/*), and finally, end the comment with an asterisk followed by a forward slash (*/). This allows you to write comments that span multiple lines

Code Example:

/*
 This is a multi-line
 comment in JavaScript.
*/

Can you explain the importance of using code comments in a collaborative programming environment?​

View Answer:
Interview Response: In collaborative programming, code comments enhance communication among developers, clarify complex logic, provide context, and document functions or variables, improving code understanding, maintainability, and overall team productivity.

What are some best practices for writing effective and clear code comments in JavaScript?​

View Answer:
Interview Response: To write effective and clear code comments, ensure conciseness and clarity. We should focus on explaining the 'why' instead of the 'what', as the code should be self-explanatory. We should use consistent commenting styles, such as single-line or multi-line comments, and avoid redundancy. Lastly, keep comments up-to-date as code evolves to prevent confusion and miscommunication.

How can comments be helpful in debugging JavaScript code?​

View Answer:
Interview Response: Comments can help identify issues, clarify intentions, and provide context during debugging, making it easier to trace problematic code sections, understand the logic, and fix errors efficiently.

Are there any disadvantages to using comments in your JavaScript code? If so, what are they?​

View Answer:
Interview Response: Disadvantages of comments include potential clutter, outdated information, and redundancy. Poorly written comments can confuse readers and hinder maintainability instead of improving code comprehension.

Can you describe the role of comments in self-documenting code, and how you can strike a balance between comments and clean, readable code?​

View Answer:
Interview Response: In self-documenting code, comments clarify complex logic or intent, while descriptive variable and function names make code readable. We can strike a balance by using comments sparingly and emphasizing clear code structure.

Code Example:

Here's an example illustrating the balance between self-documenting code and comments.

// Function to calculate the area of a rectangle
function calculateArea(length, width) {
  return length * width;
}

const length = 10;
const width = 5;

// Calculate the area of the rectangle
const area = calculateArea(length, width);

console.log(`The area of the rectangle is ${area}`);

In this example, function and variable names are descriptive, and the code is straightforward. The comments aren't necessarily needed but can be helpful for someone unfamiliar with the code. A more complex function or algorithm might require more detailed comments.

Are there any tools or extensions that can be used to help manage comments in JavaScript code? If so, please explain​

View Answer:
Interview Response: Yes, tools like JSDoc generate documentation from comments, while linters, like ESLint, enforce consistent commenting practices. We also use extensions like Comment Anchors, in VSCode, which help us navigate and organize comments effectively.

Can you give an example of when we might use a "TODO" comment?​

View Answer:
Interview Response: A "TODO" comment is used to mark incomplete features or areas requiring improvement. For example, when we may need to optimize performance by implementing a caching mechanism.

Code Example:

function calculateSum(a, b) {
    // TODO: Add input validation checks
    return a + b;
}

Can you explain the difference between using comments for documentation purposes versus using an external documentation tool like JSDoc?​

View Answer:
Interview Response: Comments provide inline explanations, while JSDoc generates external documentation using structured comments. JSDoc offers better organization, searchability, and consistency, while in-code comments aid understanding during development.