Hardcoded

What is it

Hardcoded means writing fixed values directly in source code, instead of getting them from an external source like:

• Environment variables
• Configuration files
• Database
• User input

It’s one of the most common bad practices in software development.

Pronunciation

IPA: /hɑːrd koʊdɪd/

Sounds like: “hard-koh-did” - two words combined

Accepted variants:

• Hard-coded (hyphenated)
• Hardcoded (one word)
• Hard coded (two words)

Example: The Phone Number Nobody Can Change

Hardcoded code (BAD)

// ❌ BAD: Hardcoded phone number
function sendSMS(message) {
  const phone = "+1-555-123-4567";  // 😱 Hardcoded
  smsService.send(phone, message);
}

// ❌ BAD: Hardcoded URL
function getUsers() {
  const url = "https://api.mycompany.com/users";  // 😱 Hardcoded
  return fetch(url);
}

// ❌ BAD: Hardcoded credentials (DANGEROUS)
function connectDB() {
  const password = "admin123";  // 🚨 NEVER do this
  return db.connect("admin", password);
}

Correct code (GOOD)

// ✅ GOOD: From environment variable
function sendSMS(message) {
  const phone = process.env.SMS_PHONE_NUMBER;
  smsService.send(phone, message);
}

// ✅ GOOD: From configuration
function getUsers() {
  const url = config.api.usersEndpoint;
  return fetch(url);
}

// ✅ GOOD: Credentials from environment
function connectDB() {
  const password = process.env.DB_PASSWORD;
  return db.connect(process.env.DB_USER, password);
}

Why it’s a problem

Problem	Consequence
Hard to change	Must modify code, recompile, and redeploy
Insecure	Credentials exposed in repositories
Not scalable	Different values for dev/staging/production
Hard to maintain	Values scattered throughout code
Breaks tests	Can’t easily use test values

Real-World Example: The Pizzeria and its Prices

Imagine you have an ordering system for your pizzeria.

Hardcoded approach (guaranteed problems)

# pricing.py - ❌ BAD
def calculate_total(pizzas, drinks):
    pizza_price = 15.00   # 😱 Hardcoded
    drink_price = 3.50    # 😱 Hardcoded
    tax_rate = 0.08       # 😱 Hardcoded

    subtotal = (pizzas * pizza_price) + (drinks * drink_price)
    return subtotal * (1 + tax_rate)

Problems:

1. Tax rate changes → Must find all “0.08” in code
2. Pizza promotion at $12 → Modify code, test, deploy
3. Branch in another state with different tax → Impossible

Configuration approach (flexible)

# config.py
PRICES = {
    "pizza": float(os.getenv("PIZZA_PRICE", 15.00)),
    "drink": float(os.getenv("DRINK_PRICE", 3.50)),
    "tax_rate": float(os.getenv("TAX_RATE", 0.08)),
}

# pricing.py - ✅ GOOD
from config import PRICES

def calculate_total(pizzas, drinks):
    subtotal = (pizzas * PRICES["pizza"]) + (drinks * PRICES["drink"])
    return subtotal * (1 + PRICES["tax_rate"])

Benefits:

1. Change prices without touching code
2. Different prices per environment (dev/prod)
3. Instant promotions by changing environment variables

When hardcoding IS acceptable

Sometimes fixed values make sense:

// ✅ Mathematical constants
const PI = 3.14159265359;

// ✅ Values that NEVER change
const DAYS_IN_WEEK = 7;
const HOURS_IN_DAY = 24;

// ✅ Default values (with override option)
const TIMEOUT = config.timeout || 5000;  // Default: 5 seconds

// ✅ Enums or fixed states
const STATES = {
  PENDING: "pending",
  COMPLETED: "completed",
  CANCELLED: "cancelled"
};

How to identify hardcoded code

Warning signs in your code:

🚨 Strings with full URLs
🚨 Magic numbers (42, 1000, 3600)
🚨 Credentials or tokens
🚨 Absolute file paths
🚨 Email addresses
🚨 Server names
🚨 Specific ports

How to fix it

1. Environment variables

# .env
DATABASE_URL=postgres://user:pass@localhost:5432/mydb
API_KEY=sk-1234567890
MAX_CONNECTIONS=100

2. Configuration files

// config.json
{
  "api": {
    "baseUrl": "https://api.example.com",
    "timeout": 5000
  }
}

3. Named constants

// constants.js
export const MAX_RETRY_ATTEMPTS = 3;
export const SESSION_TIMEOUT_MS = 30 * 60 * 1000; // 30 minutes

Related terms

• [[Refactoring]] - Process of improving code without changing its behavior
• [[Environment Variables]] - Variables configured outside of code
• [[Configuration Management]] - Application configuration management

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Remember: If you ever think “this will never change,” it probably will. Better to use configuration from the start.