JavaScript Animates

Which of the following statements are true about ball? 
I – ball is a local variable 
II – the ball variable in draw is different from the ball variable in start 
III – ball is a global variable 
IV – ball’s scope includes both start and draw

• III and IV
• I and II
• III only
• I, II, III, and IV

• Animates a ball by moving it down and to the right once every 20 milliseconds.
• Animates a ball by moving it up and to the right once every 20 milliseconds
• Animates a ball by moving it down and to the right every 20 seconds
• Animates a ball by moving it up and to the right once every 20 seconds

The given program animates a ball by setting a timer to move the ball across the screen. We want the animation to stop whenever the user clicks the mouse. Which statement would stop the animation in this program?

• stopTimer(ball.move(2, 2));

• stopTimer(draw);

• stopTimer(draw());

• stopTimer(draw, 20);

We extend our draw function to include the code above. How many times will the ball be moved before the animation stops?

• 2
• 20
• 25
• 40

Which of the following are techniques that make our code more reusable? 
I – Using constants instead of magic numbers 
II – Using specific values in our functions rather than using parameters 
III – Writing multiple functions that solve small subproblems rather than one function that solves the entire problem. 
IV – Writing as few lines of code as possible

• I, II, and III
• I, II, III and IV
• I and III
• II and IV

Which function has better reusability?
A: 

function drawCircle(x, y, radius, color) { var circle = new Circle(radius); circle.setPosition(x, y); circle.setColor(color); add(circle); } OR B. 
function drawGreenCircleInCenter(radius) { var circle = new Circle(radius); circle.setPosition(getWidth() / 2, getHeight() / 2); circle.setColor(Color.green); add(circle); }
 

• A
• B

How many circles of radius 10 will fit vertically stacked in a window that has height 100? The circles should not overlap, the bottom of one circle should touch the top of the next circle.

• 100
• 20
• 10
• 5

This is a circle on our canvas named ball. What are the coordinates of point A?

• ball.getX(), ball.getY()

• ball.getRadius(), ball.getY()

• ball.getX() + ball.getRadius(), ball.getY()

• ball.getX(), ball.getY() + ball.getRadius()

What statement should we use to determine if ball is hitting the bottom edge of the window?

• if(ball.getX() + ball.getRadius() < 0){ //ball is hitting bottom edge }

• if(ball.getY() - ball.getRadius() < 0){ //ball is hitting bottom edge }

• if(ball.getY() + ball.getRadius() > getHeight()){ //ball is hitting bottom edge }

• if(ball.getY() + ball.getRadius() < 0){ //ball is hitting bottom edge }

How can we determine if ball’s left edge is hitting a different shape on our canvas named box?

• if(ball == box){ //ball's left edge is hitting box }

• var elem = getElementAt(ball.getX() - ball.getRadius() - 1, ball.getY()); if(elem == box){ //ball's left edge is hitting box }

• var elem = getElementAt(ball.getX() - ball.getRadius() - 1, ball.getY()); if(elem != null){ //ball's left edge is hitting box }

• if(ball.getX() - ball.getRadius() - 1 == box){ //ball's left edge is hitting box }