How to Write Good Javascript code

JavaScript is what makes websites interactive. It's super useful. But, it can also get messy. Want to write code that's easy to read and use? This article is for you! We'll go over some best practices, helpful patterns, and why using a linter is a great idea.

Why Good JavaScript Matters

Why bother writing good JavaScript? Here's why:

• Easy to Change: Code that's easy to read is easy to update. Saves you time!
• Grows with You: As your website gets bigger, good code can handle it.
• Faster Websites: Good code runs faster. Users will thank you!
• Teamwork Makes the Dream Work: Clear code helps everyone work together.
• Fewer Oopsies: Best practices and linters help catch mistakes early.

JavaScript Best Practices: Building a Solid Foundation

These are the basics for writing great JavaScript code:

1. Strict Mode ('use strict')

Always start your JavaScript files (or functions) with 'use strict';. This helps find mistakes. It makes your code stronger.

'use strict'; function myFunction() { // Your code here }

Why use Strict Mode?

• Stops you from accidentally making global variables. Those are bad news.
• Throws errors if you try to change things you shouldn't.
• Turns some silent errors into loud, obvious errors. Good!
• No duplicate names for things. Keeps things clear.

2. Variable Declarations: const, let, and var

const, let, and var. They're different! Use them right:

• const: Use this for things that never change. Like PI.
• let: Use this for things that might change. Like someone's age.
• var: Try not to use var anymore. const and let are better.

const PI = 3.14159; let age = 30; age = 31; // That's okay! // PI = 3.14; // Nope! This will cause an error

3. Naming Conventions

Give things good names! It makes your code easier to read.

• Variables: Use camelCase. Like firstName.
• Functions: Also camelCase. Like calculateArea.
• Constants: ALL CAPS. Like MAX_SIZE.
• Classes: Start with a capital letter. Like Person.

4. Code Comments

Explain your code! Why did you do that? What's tricky? Good comments explain why, not just what.

// This function finds the area of a rectangle. // It uses the formula: area = length width function calculateArea(length, width) { return length width; }

5. Avoid Global Variables

Don't use too many global variables! They can cause problems. Keep your code organized.

6. Error Handling

What if something goes wrong? Use try...catch! This stops your website from crashing.

try { // Code that might break const result = someFunction(); } catch (error) { console.error('Something went wrong:', error); // Tell the user something went wrong, but don't crash! }

7. Asynchronous Programming: Promises and Async/Await

Getting data from the internet? That takes time! Use Promises or async/await. They make it easier to work with data that arrives later.

// Using Promises fetch('https://api.example.com/data') .then(response => response.json()) .then(data => { // Got the data! console.log(data); }) .catch(error => { // Uh oh, something went wrong console.error('Error!', error); }); // Using Async/Await async function fetchData() { try { const response = await fetch('https://api.example.com/data'); const data = await response.json(); console.log(data); } catch (error) { console.error('Error happened:', error); } } fetchData();

JavaScript Patterns: Solutions That Work

Patterns are like blueprints for common problems. They make your code easier to reuse. Easier to understand. Here are a few:

1. Module Pattern

The Module pattern keeps your code organized. It protects some parts from being changed by accident.

const myModule = (function() { let secret = 'Shhh! This is secret!'; function showSecret() { console.log(secret); } return { tellSecret: function() { showSecret(); // See the secret! } }; })(); myModule.tellSecret(); // You can see the secret this way // myModule.secret; // Error! You can't get to it directly

2. Singleton Pattern

The Singleton pattern makes sure there's only one of something. Like, maybe you only want one settings box.

const Singleton = (function() { let instance; function createInstance() { const object = new Object('Just one!'); return object; } return { getInstance: function() { if (!instance) { instance = createInstance(); } return instance; } }; })(); const one = Singleton.getInstance(); const two = Singleton.getInstance(); console.log(one === two); // They're the same!

3. Observer Pattern

The Observer pattern is like a news feed. When something changes, everyone who cares gets notified.

class Subject { constructor() { this.listeners = []; } add(listener) { this.listeners.push(listener); } remove(listener) { this.listeners = this.listeners.filter(obs => obs !== listener); } inform(data) { this.listeners.forEach(listener => listener.update(data)); } } class Listener { constructor(name) { this.name = name; } update(data) { console.log(${this.name} says: I got ${data}!); } } const subject = new Subject(); const firstListener = new Listener('First'); const secondListener = new Listener('Second'); subject.add(firstListener); subject.add(secondListener); subject.inform('News!'); // Output: // First says: I got News!! // Second says: I got News!!

JavaScript Linting: Catching Mistakes Early

JavaScript linting checks your code for mistakes. Before you even run it! It's like having a really smart friend look over your shoulder.

ESLint

ESLint is a popular linter. You can customize it to match your style. It can even automatically fix some errors!

Setting up ESLint

1. Install ESLint: npm install -g eslint or yarn global add eslint
2. Configure ESLint: Run eslint --init. Pick a style you like or make your own rules.
3. Use it in your editor: Install an ESLint plugin for your code editor.

Example ESLint Configuration (.eslintrc.js)

module.exports = { 'env': { 'browser': true, 'es6': true, 'node': true }, 'extends': 'eslint:recommended', 'parserOptions': { 'ecmaVersion': 2018 }, 'rules': { 'no-unused-vars': 'warn', // Warns you if you have variables that are declared but never used 'no-console': 'warn', // Warns you if you leave console.log() statements in your code. Good for keeping your code clean 'indent': [ 'error', 2 // Requires 2 space indentation. ], 'linebreak-style': [ 'error', 'unix' // Enforces Unix-style line breaks. ], 'quotes': [ 'error', 'single' // Enforces the use of single quotes ], 'semi': [ 'error', 'always' // Enforces semicolons at the end of statements. ] } };

This setup uses ESLint's recommended rules. It also adds rules for spaces, line breaks, quotes, and semicolons.

Conclusion: Become a JavaScript Pro

Writing great JavaScript takes time. Keep learning! Use best practices. Use patterns. Use a linter. You'll get better and better. And remember, JavaScript keeps changing! Stay up-to-date.