Premium

Like Button (Facebook-style Toggle)

By FrontendAtlas Team · Updated Jan 30, 2026

Create a Like button with toggle state and a counter in Angular. Clicking should increment on like, decrement on unlike, and never allow the count to drop below zero. The template should reflect state immediately and apply an active class when liked. Concepts: components, event…

Use a standalone Angular component as the root component.
Render a Like button with an icon, label, and a like count.

What you’ll build / What this tests

This premium angular coding focuses on Like Button (Facebook-style Toggle). You’ll apply components and event-binding thinking with easy level constraints. The prompt emphasizes Create a Like button with toggle state and a counter in Angular. Clicking should increment on….

Learning goals

Translate the prompt into a clear angular API signature and return shape.
Apply components, event-binding, state techniques to implement like button (facebook-style toggle).
Handle easy edge cases without sacrificing readability.
Reason about time/space complexity and trade-offs in angular.

Key decisions to discuss

Define the exact input/output contract before coding.
Decide on concurrency and error propagation behavior.
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

Use a standalone Angular component as the root component.
Render a Like button with an icon, label, and a like count.
Clicking the button toggles the liked state.
When liked becomes true, increase the count by 1; when unliked, decrease by 1.
Update the button visual style based on liked state.
Prevent the count from going below 0.
Initial state: not liked, count shows the initial value.
First click: becomes liked, count increases by 1, button turns 'active'.
Second click: becomes unliked, count decreases by 1, button returns to normal.
Count never becomes negative.

Mini snippet (usage only)

// Example usage
const input = /* like button (facebook-style toggle) 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.