General Clean Code Principles

Critical Rules

G5: DRY (Don't Repeat Yourself)

Every piece of knowledge has one authoritative representation.

typescript

// Bad - duplication
const taxRate = 0.0825;
const caTotal = subtotal * 1.0825;
const nyTotal = subtotal * 1.07;

// Good - single source of truth
const TAX_RATES: Record<string, number> = { CA: 0.0825, NY: 0.07 };

const calculateTotal = (subtotal: number, state: string): number => {
    return subtotal * (1 + TAX_RATES[state]);
};

G16: No Obscured Intent

Don't be clever. Be clear.

typescript

// Bad - what does this do?
return ((x & 0x0f) << 4) | (y & 0x0f);

// Good - obvious intent
return packCoordinates(x, y);

G23: Prefer Polymorphism to If/Else

typescript

// Bad - will grow forever
function calculatePay(employee: Employee): number {
    if (employee.type === "SALARIED") {
        return employee.salary;
    } else if (employee.type === "HOURLY") {
        return employee.hours * employee.rate;
    } else if (employee.type === "COMMISSIONED") {
        return employee.base + employee.commission;
    }
    throw new Error("Unknown employee type");
}

// Good - open/closed principle
interface Employee {
    calculatePay(): number;
}

class SalariedEmployee implements Employee {
    constructor(private salary: number) {}
    calculatePay(): number { return this.salary; }
}

class HourlyEmployee implements Employee {
    constructor(private hours: number, private rate: number) {}
    calculatePay(): number { return this.hours * this.rate; }
}

class CommissionedEmployee implements Employee {
    constructor(private base: number, private commission: number) {}
    calculatePay(): number { return this.base + this.commission; }
}

G25: Replace Magic Numbers with Named Constants

typescript

// Bad
if (elapsedTime > 86400) {
    // ...
}

// Good
const SECONDS_PER_DAY: number = 86400;
if (elapsedTime > SECONDS_PER_DAY) {
    // ...
}

G30: Functions Should Do One Thing

If you can extract another function, your function does more than one thing.

G36: Law of Demeter (Avoid Train Wrecks)

typescript

// Bad - reaching through multiple objects
const outputDir = context.options.scratchDir.absolutePath;

// Good - one dot
const outputDir: string = context.getScratchDir();

Enforcement Checklist

When reviewing AI-generated code, verify:

• No duplication (G5)
• Clear intent, no magic numbers (G16, G25)
• Polymorphism over conditionals (G23)
• Functions do one thing (G30)
• No Law of Demeter violations (G36)
• Boundary conditions handled (G3)
• Dead code removed (G9)