Premium

React Shopping Cart Mini

By FrontendAtlas Team · Updated Jan 30, 2026

Build a small shopping cart UI in React. Show a list of products, let the user add them to the cart, adjust quantities, remove items, and display derived totals for item count and price. React focus: use immutable updates for cart lines and derived totals.…

Render a list of products with name, price, and an "Add to…
Maintain a cartItems collection where each item has id, name, price, and…

What you’ll build / What this tests

This premium react coding focuses on React Shopping Cart Mini. You’ll apply react and state thinking with hard level constraints. The prompt emphasizes Build a small shopping cart UI in React. Show a list of products, let the user….

Learning goals

Translate the prompt into a clear react API signature and return shape.
Apply react, state, arrays techniques to implement react shopping cart mini.
Handle hard edge cases without sacrificing readability.
Reason about time/space complexity and trade-offs in react.

Key decisions to discuss

Define the exact input/output contract before coding.
Choose iteration vs higher-order methods for readability.
Prioritize predictable edge-case handling over micro-optimizations.

Evaluation rubric

Correctness: covers required behaviors and edge cases.
Clarity: readable structure and predictable control flow.
Complexity: avoids unnecessary work for large inputs.
API discipline: no mutation of inputs; returns expected shape.
Testability: solution is easy to unit test.

Constraints / Requirements

Render a list of products with name, price, and an "Add to cart" button for each.
Maintain a cartItems collection where each item has id, name, price, and quantity.
In the cart, show each item's name, unit price, quantity, and line total (price * quantity).
Provide controls to increase and decrease quantity for each cart item.
Allow removing an item from the cart entirely.
Display derived values: total item count and total cart price.
Visually stack the cart card *under* the products card (single-column layout).
Clicking "Add to cart" for a product that is not yet in the cart adds it with quantity…
Clicking "Add to cart" again for the same product increases its quantity by 1.
Clicking the "+" button in the cart increases that item's quantity by 1.

Mini snippet (usage only)

// Example usage
const input = /* react shopping cart mini input */;
const result = solve(input);
console.log(result);

// Edge case check
const empty = input ?? null;
const fallback = solve(input);
console.log(fallback);

// Expected: describe output shape, not the implementation
// (no solution code in preview)

Common pitfalls

Mutating inputs instead of returning a new value.
Skipping edge cases like empty input, duplicates, or nulls.
Overlooking time complexity for large inputs.