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hardMachine Coding

Build a Canvas Drawing Board

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01

Understand the problem

Build a freehand drawing board on canvas with undo and colors.

ReactCanvasPointer
02

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

Nudge consolestandby

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03

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Building a Canvas Drawing Board in React

Mental model: Get the canvas 2D context once via a ref. Pointer events drive a tiny state machine: pointerdown starts a stroke (beginPath + moveTo), pointermove while drawing extends it (lineTo + stroke), pointerup ends it. Brush colour/size are just contex

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04

React solution

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

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

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Transmission complete // awaiting log

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Dossier 76 of 87 decoded in the Frontend Machine Coding track. One more won't hurt.

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