JavaScript code:

// Type your code in here.

class TreeTurtle extends Turtle {
  polygon(sides: number, sideLength: number) {
    let count = 0;
    while (count < sides) {
      count++;
      this.move(sideLength);
      this.turnLeft(1 / sides);
    }
  }

  branch(length: number){
    if (length < 10){
      return;
    }

    this.penColor('brown');
    this.penWidth(length / 10);

    this.move(length / 2);
    this.turnRight(1/50);
    this.move(length / 2);

    let left = new TreeTurtle(this);
    left.turnLeft(about(1/8));
    left.branch(about(length * .75));

    let right = new TreeTurtle(this);
    right.turnRight(about(1/12));
    right.branch(about(length * .75));
  }
}

function about(n:number){
  return n * ( 1 - 0.1 * Math.random());
}

let t = new TreeTurtle();
t.penUp();
t.move(200);
t.penDown();
t.turnLeft(1/2);
t.branch(200);