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React Progress Bar (0–100 with Threshold Colors)

By FrontendAtlas Team · Updated Jan 30, 2026

Build a React progress bar for values 0–100 with +10%/−10% controls. Clamp progress to the valid range and change the bar color by thresholds (e.g., red 66). Show the numeric percentage and keep the UI in sync with state. React focus: derive classes from state…

Render the progress bar UI as the main component.
Display the current progress percentage (e.g., "40%").

What you’ll build / What this tests

This premium react coding focuses on React Progress Bar (0–100 with Threshold Colors). You’ll apply react and state thinking with easy level constraints. The prompt emphasizes Build a React progress bar for values 0–100 with +10%/−10% controls. Clamp progress to the valid….

Learning goals

Translate the prompt into a clear react API signature and return shape.
Apply react, state, event-handlers techniques to implement react progress bar (0–100 with threshold colors).
Handle easy 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.
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 the progress bar UI as the main component.
Display the current progress percentage (e.g., "40%").
Provide "-10%" and "+10%" buttons to decrease/increase progress by 10.
Clamp progress so it never goes below 0 or above 100.
Change the bar color based on thresholds (red/orange/green).
Initial progress starts at 0%.
Clicking "+10%" increases progress by 10 up to 100.
Clicking "-10%" decreases progress by 10 down to 0.
Progress never renders below 0% or above 100%.
Bar color changes by thresholds (example: 66 green).

Mini snippet (usage only)

// Example usage
const input = /* react progress bar (0–100 with threshold colors) 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.