Q: How do you calculate the cart total correctly in a food ordering app?

Sum price * quantity for each item: Object.entries(cart).reduce((sum, [id, qty]) => { const item = menu.find(m => m.id === parseInt(id)); return sum + item.price * qty; }, 0). Remember to parseInt the ID and multiply price by quantity.

Question 1

Should you use a single state object in a food ordering app?

Accepted Answer

Yes. Use one state object: { cart, searchQuery, filters }. All views read from this state. All actions update this state. This makes the app predictable and debuggable. Scattered state variables lead to bugs.

Question 2

What are common mistakes when building a food ordering app in an interview?

Accepted Answer

Not handling empty cart or no results, allowing negative quantity, incorrect total calculation, spending too much time on CSS, scattered state, not debouncing search, and not testing. Fix each with the appropriate technique.

Question 3

How do you avoid negative quantity in a food ordering app cart?

Accepted Answer

When decrementing, check if the quantity drops to 0 or below. If so, delete the item from the cart: if (cart[id] <= 0) delete cart[id]. This prevents negative quantities and keeps the cart clean.

Question 4

How do you calculate the cart total correctly in a food ordering app?

Accepted Answer

Sum price * quantity for each item: Object.entries(cart).reduce((sum, [id, qty]) => { const item = menu.find(m => m.id === parseInt(id)); return sum + item.price * qty; }, 0). Remember to parseInt the ID and multiply price by quantity.

Should you use a single state object in a food ordering app?

More FAQs in Food Ordering App: Common Mistakes in Interviews

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