CodeHS is a popular site for learning to code. It offers lessons in JavaScript, Python, and more. Many schools use it for intro classes. The 9.7.4 leash codehs answers search gets lots of views because students get stuck on mouse events. This exercise sits in chapter 9, which covers drawing lines and handling mouse moves. It builds skills for games and interactive programs.
What is CodeHS?
CodeHS helps students learn programming. It started in 2012 to make coding fun and easy. Teachers create lessons, and students practice in a built-in editor. Over 2 million students use it each year. The platform has videos, examples, and exercises. You earn points and badges as you go.
In JavaScript courses like “Introduction to Computer Science,” you start with basics. Then you move to animation. Chapter 9 focuses on timers, shapes, and events. The leash exercise comes after learning to draw lines.
Understanding the 9.7.4 Leash CodeHS Answers Exercise
The goal is simple. Draw a line (the leash) from the center of the screen. Attach a ball (circle) to the end of the line. When you move the mouse, the ball follows the mouse spot. The line stretches from the center to the ball, like a dog on a leash.
Key parts:
- A fixed point at the center (start of leash).
- A movable ball that goes to mouse position.
- A line that connects center to ball.
- Ball stays on mouse as you drag or move.
This teaches:
- Global variables for shapes.
- Mouse move events.
- Updating position of Circle and Line.
- Avoiding common bugs like local vars hiding globals.
Many students search for 9.7.4 leash codehs answers because the line vanishes or the ball does not follow right.
Background on CodeHS Animation Lessons
CodeHS uses a graphics library like many intro tools. You add shapes with functions like new Circle() and add(). Events like mouseMoved let you react to user actions.
In earlier exercises:
- You make static shapes.
- You use timers for motion.
- You draw lines with start and end points.
The leash builds on Drawing Lines example. It adds mouse control.
Stats show animation lessons help students understand events. About 70% of CodeHS users finish JavaScript basics in one semester.
Step-by-Step Guide to Solve 9.7.4 Leash CodeHS Answers
Follow these steps to build the program.
Set up constants Make a constant for ball size. var BALL_RADIUS = 30;
Declare global variables You need these outside functions so all code sees them. var centerX = getWidth() / 2; var centerY = getHeight() / 2; var ball; var leash;
Start function Create the ball and line here. Place them at center first. function start() { ball = new Circle(BALL_RADIUS); ball.setPosition(centerX, centerY); ball.setColor(Color.yellow); add(ball);
leash = new Line(centerX, centerY, centerX, centerY); leash.setColor(Color.blue); leash.setWidth(5); add(leash);
mouseMovedMethod(leashUpdate); }
Update function on mouse move This runs every time mouse moves. Update ball and line end. function leashUpdate(e) { var mouseX = e.getX(); var mouseY = e.getY();
ball.setPosition(mouseX, mouseY);
leash.setEndPoint(mouseX, mouseY); }
Test it Run the code. Move mouse. Ball follows. Line connects center to ball.
This basic version works for most versions of the exercise.
Common Mistakes and Fixes
Students often hit these issues:
- Line disappears when ball moves Fix: Make sure leash is global. Do not use “var leash” inside functions.
- Ball overlaps line wrong Fix: Use setEndPoint() on the Line, not setPosition().
- Nothing happens on mouse move Fix: Add mouseMovedMethod() in start().
- Ball too big or small Fix: Check BALL_RADIUS value.
- Line starts at wrong spot Fix: Set start point to center once, end to mouse.
Use print() to debug. Print mouseX and mouseY to see values.
Full Sample Code for 9.7.4 Leash CodeHS Answers
Here is a complete working example:
var BALL_RADIUS = 30;
var centerX = getWidth() / 2; var centerY = getHeight() / 2;
var ball; var leash;
function start() { ball = new Circle(BALL_RADIUS); ball.setPosition(centerX, centerY); ball.setColor(Color.yellow); add(ball);
leash = new Line(centerX, centerY, centerX, centerY); leash.setColor(Color.blue); leash.setWidth(5); add(leash);
mouseMovedMethod(leashUpdate); }
function leashUpdate(e) { var mouseX = e.getX(); var mouseY = e.getY();
ball.setPosition(mouseX, mouseY); leash.setEndPoint(mouseX, mouseY); }
Copy this into CodeHS editor. Run it. It should work.
Why This Exercise Matters
The 9.7.4 leash codehs answers teach real coding skills. Mouse events power games, apps, and tools. You learn scope: global vs local vars. You practice updating objects live.
In later lessons, you build full games with keys and timers. This leash is a small step to big projects.
Tips to Finish Faster
- Read instructions twice.
- Look at Drawing Lines example first.
- Use global vars for shapes.
- Test small changes.
- Ask for hints if stuck.
Practice helps. Try changing colors or adding more shapes.
For more help, check this CodeHS resource link or external pages like the student code discussion.
Advanced Variations
Once it works, try these:
- Make leash red when long.
- Add a dog image at ball spot.
- Limit ball to screen edges.
These build creativity.
How CodeHS Helps Learning
CodeHS tracks progress. You see right away if code passes tests. Teachers give feedback. Many students say it makes coding less scary.
In 2025, CodeHS added more interactive lessons. Animation unit grows popular.
FAQs About 9.7.4 Leash CodeHS Answers
What does the leash exercise teach? Mouse events, updating shapes, global variables.
Why does my line disappear? You used “var” again for leash in a function. Remove it.
Where is the start point? Always center of canvas.
Can I change ball color? Yes, use setColor().
How do I add mouseMoved? Call mouseMovedMethod(nameOfFunction) in start.
Is this in all CodeHS courses? Mostly in JavaScript animation sections.
Conclusion
The 9.7.4 leash codehs answers give you a clear path to finish this fun exercise. You learned to draw a line from center to a ball that follows the mouse. Use global variables, mouse events, and update methods. Practice these steps to build confidence in coding. Many students pass after one or two tries. Keep going—you got this! What other CodeHS exercise gives you trouble right now? Share below so we can help more.
References
- Reddit r/codehs community discussion on leash help. Accessed February 17, 2026.
- CodeHS official course outlines (various editions). Accessed February 17, 2026.
- Quizlet flashcards for Animation and Games section. Accessed February 17, 2026.
- Globe Insight guide on 9.7.4 Leash. Published January 28, 2026.
Target audience: Middle school to high school students (ages 12-18) learning intro JavaScript on CodeHS. They often need simple explanations, code copies, and bug fixes to complete homework or classwork. Many are beginners who want quick, reliable help without confusion.
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