title: from JavaScript to React class
body: <p>can someone help me to change this JS code to React class? </p>
  
  <pre><code>function Ball(x, y, radius) {
      this.radius = radius;
      this.dx = randomDx();
      this.dy = randomDy();
      this.mass = this.radius * this.radius * this.radius;
      this.x = x;
      this.y = y;
      this.color = randomColor();
      this.draw = function() {
          ctx.beginPath();
          ctx.arc(Math.round(this.x), Math.round(this.y), this.radius, 0, 2*Math.PI);
          ctx.fillStyle = this.color;
          ctx.fill();
          ctx.strokeStyle = 'rgba(0, 0, 0, 0.6)';
          ctx.stroke();
          ctx.closePath();
      };
      this.speed = function() {
          // magnitude of velocity vector
          return Math.sqrt(this.dx * this.dx + this.dy * this.dy);
      };
      this.angle = function() {
          //angle of ball with the x axis
          return Math.atan2(this.dy, this.dx);
      };
      this.onGround = function() {
          return (this.y + this.radius &gt;= canvas.height)
      }
  }
  </code></pre>
  
  <p>This code is intended to show balls in the canvas that collide with each other and change their direction and speed (like real balls). My problem is that I cannot correctly change the JavaScript code to React.</p>