How to Write Clean, Readable JavaScript Code: Essential Practices

Introduction

This series examines how to write clean JavaScript/TypeScript code, presenting techniques every programmer should know and apply.

Key Concepts

Code smells and refactoring

“Code smells are a surface indication of deeper problems in a system.” – Martin Fowler

“Code smells are a source of technical debt.” – Robert C. Martin

Both authors agree that code smells trigger system issues, while technical debt creates long‑term maintenance burdens.

Technical debt

Technical debt arises when developers compromise optimal solutions for short‑term speed, incurring future work to repay the debt, much like financial debt.

Code refactoring is the process of restructuring existing code without changing its external behavior.

Improves non‑functional attributes

Enhances readability and reduces complexity

Increases maintainability

Creates clearer structure for better scalability

Before You Start

Effective teamwork requires certain guidelines.

Code Readability

Code must be readable by humans; the longest part of development is reading code, not writing it.

Consider the following three array definitions and ask which is most readable.

const users = [{ id: 1, name: "Carlos Caballero", memberSince: "1997-04-20", favoriteLanguageProgramming: ["JavaScript", "C", "Java"] }, { id: 2, name: "Antonio Villena", memberSince: "2014-08-15", favoriteLanguageProgramming: ["Go", "Python", "JavaScript"] }, { id: 3, name: "Jesús Segado", memberSince: "2015-03-15", favoriteLanguageProgramming: ["PHP", "JAVA", "JavaScript"] }];

Writing Code in English

Even non‑native speakers should write code in English because it is the lingua franca of software development; reading code written in an unfamiliar language is like deciphering encrypted text.

const benutzer = { id: 1, name: "John Smith", mitgliedVon: "1997-04-20" }; // German
Gehaltserhöhung(benutzer, 1000);

const użytkownik = { id: 1, imię: "John Smith", członekZ: "1997-04-20" }; // Polish
wzrostWynagrodzeń(użytkownik, 1000);

const user = { id: 1, name: "John Smith", memberSince: "1997-04-20" }; // English
increaseSalary(user, 1000);

Team Collaboration

Modern development relies on teams, not solitary programmers. Common debates include spaces vs. tabs, brace placement, and semicolon usage, but tools enforce consistent style.

Use a shared .editorconfig file to define formatting rules across IDEs.

root = true

[*]
end_of_line = lf
insert_final_newline = true

[*.{js,py}]
charset = utf-8

[*.py]
indent_style = space
indent_size = 4

[Makefile]
indent_style = tab

[*.js]
indent_style = space
indent_size = 2

[{package.json,.travis.yml}]
indent_style = space
indent_size = 2

Linters enforce these rules; for example, an ESLint configuration:

{
  "globals": { "myModule": true },
  "env": { "browser": true },
  "rules": {
    "no-unused-vars": "error",
    "quotes": ["warning", "double"]
  }
}

Tools like Prettier automatically format code according to linter settings, allowing developers to focus on solving real problems.

Conclusion

The article summarizes essential points before writing clean code, applicable to any developer:

Write code that people can understand. Readability reduces the time spent deciphering code.

Write code in English. It is the universal language for sharing code worldwide.

Collaborate as a team. Establish common rules and use tools so the codebase appears as if written by a single author.