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easyMachine Coding

Build a Stopwatch

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01

Understand the problem

Build a stopwatch with start, pause, resume and reset.

ReactTimersState
02

Attempt it yourself

Sketch your approach before reading the solution — that's what interviews test.

Nudge consolestandby

Stuck? Beam a request up — the console returns a conceptual nudge that guides your logic without spoiling the implementation.

03

Study the solution

Solve in

Building a Stopwatch in React

Mental model: Don't accumulate time by adding a fixed amount each tick — that drifts. Instead store a start timestamp and, on every frame, compute elapsed = now - start. State holds the elapsed milliseconds; a ref holds the start time and the animation handle so they survive

Solution ready — 2 min read

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04

React solution

Complete solutionRun Playground
import React from 'react';
import Stopwatch from './src/Stopwatch';

export default function App() {
  return (
    <div style={{ fontFamily: 'sans-serif', padding: 20 }}>
      <h1>Stopwatch Demo</h1>
      <Stopwatch />
    </div>
  );
}
05

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Transmission complete // awaiting log

KEEP THE
STREAK ALIVE.

Dossier 15 of 87 decoded in the Frontend Machine Coding track. One more won't hurt.

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