Refactoring Safely With AI

Change Shape, Keep Behavior

Refactoring means improving the structure of code without changing what it does. Renaming for clarity, splitting one big function into small ones, moving code to a better file. AI is very good at these mechanical tasks because they rarely require new ideas.

The safety net first

1. Make sure you have tests that pass before touching anything
2. If no tests exist, ask the AI to help write a few
3. Commit your changes to git so you can roll back
4. Only then start refactoring

Three refactors AI does well

// Before: one long function doing too much function processOrder(order) { if (!order.email.includes("@")) throw new Error("bad email"); const tax = order.total * 0.08; const shipping = order.total > 50 ? 0 : 9.99; const final = order.total + tax + shipping; db.save({ order, final }); sendEmail(order.email, `Total: ${final}`); } // After: small, named functions a human can read function validateOrder(order) { if (!order.email.includes("@")) throw new Error("bad email"); } function calculateTotal(order) { const tax = order.total * 0.08; const shipping = order.total > 50 ? 0 : 9.99; return order.total + tax + shipping; } function processOrder(order) { validateOrder(order); const final = calculateTotal(order); db.save({ order, final }); sendEmail(order.email, `Total: ${final}`); }Extract-function is the most common refactor. AI handles it cleanly when you ask for it.

Refactor prompts that work

• Rename `x`, `y`, `z` to descriptive names based on how they are used
• Extract the validation block into a function called `validateOrder`
• Move these helper functions into a new file called `utils/pricing.ts`
• Replace the switch statement with a lookup map

When to stop

Every refactor has a diminishing return. Rename until names are clear. Extract until functions fit on one screen. Stop when the next change would be a matter of taste, not clarity.

Refactoring is a surgical act. AI hands you the scalpel, but you still choose where to cut.

— A team lead

The big idea: refactoring is safe when behavior is pinned down by tests and changes are small. AI is ideal for mechanical restructuring, but you own the safety net.