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Reusable Child Component with @Input/@Output (Two-way Binding)

By FrontendAtlas Team · Updated Jan 30, 2026

Expose a value input and a valueChange output to support two-way binding, and keep the child component stateless so the parent owns the source of truth. Concepts: components, inputs outputs, binding, event binding, template syntax.

Create a reusable child component (standalone) that receives value via @Input.
Child must emit changes via @Output so the parent can react.

What you’ll build / What this tests

This premium angular coding focuses on Reusable Child Component with @Input/@Output (Two-way Binding). You’ll apply components and inputs-outputs thinking with easy level constraints. The prompt emphasizes Expose a value input and a valueChange output to support two-way binding, and keep the child….

Learning goals

Translate the prompt into a clear angular API signature and return shape.
Apply components, inputs-outputs, binding techniques to implement reusable child component with @input/@output (two-way binding).
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.
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

Create a reusable child component (standalone) that receives value via @Input.
Child must emit changes via @Output so the parent can react.
Implement two-way binding pattern: value + valueChange (so parent can use [(value)]).
Parent component must demonstrate:
- Property binding: [label]="..." and [value]="..."
- Event binding: (valueChange)="..." or [(value)]="..."
UI should include an input + a button inside the child. Child emits updated value when user edits…
Typing in the child input updates the parent's state (via two-way binding).
Clicking child button emits an event that the parent logs/increments a counter.
Parent can also update the value programmatically and child reflects it.

Mini snippet (usage only)

// Example usage
const input = /* reusable child component with @input/@output (two-way binding) 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.