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Ever looked at a function and felt lost in its complexity? Let's explore a fundamental principle of clean code: functions should maintain only one level of abstraction.
Here's a real-world example of user creation in a web application:
// ❌ A function doing too many things at different abstraction levels function createUser(userData) { // Validate data if (!userData.email || !userData.email.includes('@')) { return 'Invalid email'; } if (userData.password.length < 8) { return 'Password too short'; } // Hash password const salt = generateSalt(); const hashedPassword = hashWithSalt(userData.password, salt); // Format user data const user = { email: userData.email.toLowerCase(), password: hashedPassword, salt: salt, createdAt: new Date() }; // Save to DB saveUserToDatabase(user); }
This function mixes different levels of abstraction:
Let's refactor it following the single level of abstraction principle:
// ✅ Clean version with one level of abstraction function createUser(userData) { const validationError = validateUserData(userData); if (validationError) return validationError; const securePassword = hashPassword(userData.password); const formattedUser = formatUserData(userData.email, securePassword); return saveUserToDatabase(formattedUser); } function validateUserData({ email, password }) { if (!email || !email.includes('@')) return 'Invalid email'; if (password.length < 8) return 'Password too short'; return null; } function hashPassword(password) { const salt = generateSalt(); return { hash: hashWithSalt(password, salt), salt }; } function formatUserData(email, securePassword) { return { email: email.toLowerCase(), password: securePassword.hash, salt: securePassword.salt, createdAt: new Date() }; }
When writing functions:
Remember: If you're mixing "how" and "what" in the same function, you're probably dealing with multiple levels of abstraction. Split them up!
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