React

by michael_t

HTML

<div id="app"></div>

CSS

body {
  background: #20262E;
  padding: 20px;
  font-family: Helvetica;
}

#app {
  background: #fff;
  border-radius: 4px;
  padding: 20px;
  transition: all 0.2s;
}

/* #example {
  background-color: blue;
} */

canvas {
  background-color: blue;
}

li {
  margin: 8px 0;
}

h2 {
  font-weight: bold;
  margin-bottom: 15px;
}

.done {
  color: rgba(0, 0, 0, 0.3);
  text-decoration: line-through;
}

input {
  margin-right: 5px;
}

React

class Canvas extends React.Component {
	constructor(props) {
    super(props);

    this.state = { x: 0, y: 0 };
  }
  
  componentDidMount() {
    const canvas = this.refs.canvas
    const ctx = canvas.getContext("2d")

    ctx.fillRect(25, 25, 100, 100);
    ctx.clearRect(45, 45, 60, 60);
    ctx.strokeRect(50, 50, 50, 50);
  }
  
  _onMouseMove(e) {
    this.setState({ x: e.screenX, y: e.screenY });
    console.log("x: " + this.state.x + " y: " + this.state.y);
    
    var canvas = this.refs.canvas;
    var ctx = canvas.getContext("2d");
    var data = ctx.getImageData(this.state.x, this.state.y, 1, 1).data;
    console.log(data);
  }
  
  render() {
    return(
      <div >
        <canvas onMouseMove={this._onMouseMove.bind(this)} ref="canvas" width={640} height={425} />
      </div>
    )
  }
}

ReactDOM.render(<Canvas />, document.querySelector("#app"))