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Coding Style - JavaScript Interview Questions

Code Quality: Code Style

When it comes to coding style and application development, what is the goal?​

View Answer:
Interview Response: The goal is to take a complex task and code it correctly and in a human-readable manner.

Technical Response: The goal of coding style and application development is to create maintainable, efficient, and readable code, ensuring optimal functionality, collaboration, and ease of understanding for developers and users alike.
note

Several code styling guides help programmers reach this goal.

Here's a table of some commonly used style guides in web development:

Style GuideURL
Airbnb JavaScript Style GuideLink
Google JavaScript Style GuideLink
Google HTML/CSS Style GuideLink
Mozilla CSS Style GuideLink
W3C's CSS GuidelinesLink
Idiomatic.js (Principles of JavaScript Style)Link
Bootstrap CSS Code GuideLink
StandardJS (JavaScript Style Guide, Linter, and Formatter)Link
note

Please note that you should follow the style guide recommended or required by your team, project, or organization. Also, note that the URLs above were valid as of my last training data in September 2021 and might have changed since.

Should you always use curly braces with conditional if statements?​

View Answer:
Interview Response: Using curly braces with a conditional if statement is not required, but it's a best practice to improve readability and prevent errors.

Code Example:

// conditional if statement
if (n < 0) {
  console.log(`Power ${n} is not supported`);
} else {
  console.log(`Power ${n} is supported`);
}

Should code lines in JavaScript be long and horizontal or split into separate lines? Provide a justification for your decision​

View Answer:
Interview Response: Code lines in JavaScript should be split into separate lines, ideally not exceeding 80 to 100 characters. This improves readability, reduces horizontal scrolling, and makes the code easier to understand and maintain. It is also a best practice.

Code Example: Proper Implementation

// backtick quotes (`) allow splitting the string into multiple lines
let str = `
  ECMA International's TC39 is a group of JavaScript developers,
  implementers, academics, and more collaborating with the community
  to maintain and evolve the definition of JavaScript.
`;

// Conditional If statement variable conditions split in multiple lines
if (id === 123 && moonPhase === 'Waning Gibbous' && zodiacSign === 'Libra') {
  letTheSorceryBegin();
}
note

A great example would be long paragraphs longer than 120 characters. We can use backticks to handle lines longer than 120 characters.

What do development teams typically agree to for the maximum character length?​

View Answer:
Interview Response: In JavaScript, development teams typically agree on a maximum character length of 80 to 100 characters per line, as it strikes a balance between readability and efficient use of screen space while coding.

Code Example: Proper Implementation

// backtick quotes (`) allow splitting the string into multiple lines
let str = `
  ECMA International's TC39 is a group of JavaScript developers,
  implementers, academics, and more collaborating with the community
  to maintain and evolve the definition of JavaScript.
`;

What is a best practice for vertical space of code?​

View Answer:
Interview Response: A best practice for vertical space in JavaScript includes using blank lines to separate logical sections, function declarations, and blocks of related code, improving readability and code organization.

Code Example:

function pow(x, n) {
  let result = 1;
  //              <--
  for (let i = 0; i < n; i++) {
    result *= x;
  }
  //              <--
  return result;
}

What is one way to reduce nesting levels in your code?​

View Answer:
Interview Response: One way to reduce nesting levels in JavaScript is to refactor nested if statements and loops by using early returns, switch statements, and function extraction to break down complex logic into smaller, simpler pieces.

Here are some rules of thumb for reducing nesting in your code:

  1. Keep your conditional blocks brief. Keeping things local improves readability.
  2. Think about restructuring if your loops and branches are more than two layers deep.
  3. Consider separating layered logic into distinct functions. For example, you may write a function to handle each item instead of using a double nested loop to cycle through a list of objects containing a list (such as a protocol buffer with repeated fields).

The two constructs below are identical:

function pow(x, n) {
  if (n < 0) {
    console.log("Negative 'n' not supported");
  } else {
    let result = 1;

    for (let i = 0; i < n; i++) {
      result *= x;
    }

    return result;
  }
}

This is proper way to avoid nesting:

function pow(x, n) {
  if (n < 0) {
    console.log("Negative 'n' not supported");
    return;
  }

  let result = 1;

  for (let i = 0; i < n; i++) {
    result *= x;
  }

  return result;
}

What is the purpose of a linter in JavaScript?​

View Answer:
Interview Response: A linter in JavaScript helps identify potential errors, enforce coding conventions, improve code quality, maintain consistency, and provide suggestions for best practices during development.
note

The great thing about linters is that style-checking can also find bugs, like typos in variable or function names. Because of this feature, using a linter is recommended even if you do not want to stick to one particular code style.

How does the use of semicolons contribute to a clean and organized JavaScript code?​

View Answer:
Interview Response: Semicolons help in maintaining a clean and organized code base, by explicitly indicating the end of a statement. This eliminates ambiguity and makes the code easier to read and understand.

What is the significance of indentation in JavaScript?​

View Answer:
Interview Response: Indentation is essential in JavaScript for improving code readability and maintainability. It helps to visually separate blocks of code, making it easier to understand the flow and structure of the program.

How can you ensure consistent code style across your JavaScript project?​

View Answer:
Interview Response: To ensure consistent code style across a project, you can use tools like ESLint or Prettier. These tools help to enforce a specific set of conventions and automatically format the code according to the predefined rules. Additionally, having a well-documented style guide and conducting regular code reviews can also help maintain consistency.