CodeHS Unit 9 Test - Animations and Games

In the following code, when will the function draw be called?

• Once, inside of start

• Never

• Every 20 milliseconds

• Every 20 seconds

What does this program do?

• Draws 1 randomly sized circle at a random place on the canvas.

• Draws several randomly sized circles at random places on the canvas by drawing 1 every 50 milliseconds.

• Draws 1 randomly colored circle at the center of the canvas.

• Draws several randomly colored circles at the center of the canvas by drawing 1 every 50 milliseconds.

Why do we want our code to be “reusable”?

• To avoid writing similar code multiple times

• To avoid solving the same problem over and over again

• To save time

• All of these are correct.

How can we make our code reusable?

• Use constants instead of magic numbers

• Use parameters in our functions instead of specific values

• Write multiple functions that solve small subproblems rather than one function that solves the entire problem.

• All of these are correct.

Which function has better reusability?

• 
• 

This is a Circle object on our canvas named ball. Point A is on the far left edge of the circle. How can we calculate the x-coordinate of point A?

• ball.getX() - ball.getRadius();

• ball.getY() + ball.getRadius();

• ball.getX() + ball.getRadius();

• ball.getX();

Suppose we’ve written a function drawCircle that we want to call every time the mouse is clicked. How can we do this?

• mouseClickMethod(drawCircle(e));

• if(mouseClickMethod){

  drawCircle();

  }

• mouseClickMethod(drawCircle);

• mouseClickMethod(drawCircle());

What is a callback function?

• A function passed to an event handler that is called every time a certain event happens

• A function that is never called

• A function called at the bottom of the start function

• A function called every 20 milliseconds

Which statement will call the function paint every time the mouse is moved?

• mouseDragMethod(paint);

• mouseDownMethod(paint);

• mouseMoveMethod(paint);

• mouseMoveMethod(paint(e));

This code from the video draws lines on the canvas when the mouse is pressed down and dragged. But there is one problem. What is wrong with the following code?

• Lines 14 and 15 are registering the mouse events incorrectly

• Line 5 adds a line to the screen every time the mouse is down, but we need a line added before any mouse events

• Line 4 declares a new local variable var line. The local variable line in down is different from the global variable line in drag, but we need these functions to be affecting the same line

• None, there is no problem