Introduction to Coding

Introduction
to
coding
using JavaScript and codeguppy.com

Part I: Introduction
• About codeguppy.com
• Creating accounts in codeguppy.com
• Environment overview
Part II: Steps into coding
• Drag and drop coding
• Drawing with code
• Animations
Agenda

codeguppy.com
About codeguppy.com
• Online coding platform for kids, teens and
code newbies
• Text-based coding
• JavaScript language
• Based on p5.js (Processing API)
• Code animations, games and other fun
programs
• Built-in assets (backgrounds, sprites, etc.)
• Tons of projects. Browse – Remix – Share
• Free!

Why learn JavaScript?
• JavaScript is a super-popular real-world programming language
used both by beginners but also by professional software
developers. (The entire codeguppy.com was coded in JavaScript)
• People use JavaScript to build websites, online games and do
creative coding. On codeguppy.com, you can use JavaScript to draw
with code, implement animations, build games and other fun
projects.
• Coding in a text-based language such as JavaScript has also other
benefits beyond the world of programming. It enhances problem-
solving skills but also attention to details.

Programming is like
writing a book...
… except if you miss out a
single comma on page 349
the whole thing you wrote
makes no sense.
- Anonymous

codeguppy.com
Let’s open an account with codeguppy.com
• codeguppy.com gives you unlimited space in the cloud to write and
store tons of programs
• But first you need to open an account with codeguppy.com
• You need to provide a valid email address and a password (website
doesn’t ask any other personal details)
Note: After registration, you should get an email from codeguppy.com.
Please verify your email by clicking the link in the email.
JOIN FOR FREE
Email:
Password:
REGISTER NOW
Register with email
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2
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Code Editor
Type here your
program
Assets Toolbar
Browse sprite
library, colors,
etc.
Run / Stop Button
Run or Stop your program.
Output Canvas
Here you’ll see the
output of your
program.

Let’s play with built-in assets
sprite('adventure_girl.idle', 400, 300, 0.5); sprite('knight.idle', 400, 300, 0.5);
You don’t have to write the above code. Just drag and drop a sprite from the palette in the code editor to have this code generated for you.

music('Fun Background');
background('Field');
sprite('plane.fly', 400, 300, 0.5);
Build a program using drag-and-drop
Step 1: Drag and drop a music
file
Step 2: Drag and drop a
background image or color
Step 3: Drag and drop a sprite
Press “Play” when ready.

Built-in instruction that asks
computer to display a sprite on
the canvas.
The actual sprite is specified in
between quotes inside the
parenthesis as a “parameter”.
Parameters of the instruction.
Parameters specify what sprite to display, where to
display it on the canvas and at what coordinates.
Experiment: Try to change the 400 and 300
numbers with other numbers between 0 and 800.
Press “Play” / “Stop”
after each
modification to run /
stop the program.
sprite('adventure_girl.idle', 400, 300, 0.5);

• Programs can write and draw on a graphical canvas of 800x600 pixels
• Origin is in the top-left corner
• Middle of the canvas is at about (400, 300)
• x coordinate goes from 0 to 800 (left to right)
• y coordinate goes from 0 to 600 (top to bottom)
(400, 300)
Output canvas

Our first type-in program
circle(400, 300, 300);
• Type carefully this line in the
code editor.
• Make sure you use the same
casing as illustrated and
include all the punctuation
signs.
• When ready, press the Play /
Run button

circle(400, 300, 300);
Built-in instruction that asks
computer to draw a circle on the
canvas.
codeguppy.com has many built-
in instructions for different
purposes (remember the sprite
instruction used before).
Parameters of the instruction.
There are 3 parameters inside
parenthesis and separated by comma:
- 400, 300 - coordinates of circle
center
- 300 – radius of the circle
Try to modify the
parameters of this
instruction and
notice the effect.
Don’t forget to press
“Play” / “Stop” after
each modification.

codeguppy.com/code.html
// Draw bear face
circle(400, 300, 200);
// Draw left ear
circle(250, 100, 50);
circle(270, 122, 20);
// Draw right ear
circle(550, 100, 50);
circle(530, 122, 20);
// Draw left eye
circle(300, 220, 30);
circle(315, 230, 10);
// Draw right eye
circle(500, 220, 30);
circle(485, 230, 10);
// Draw nose
circle(400, 400, 90);
circle(400, 350, 20);
Multiple instructions
in a program

Other graphical instructions
circle(400, 300, 200);
ellipse(400, 300, 300, 200);
rect(400, 300, 300, 200);
line(400, 300, 500, 500);
triangle(400, 100, 200, 400, 600, 500);
arc(400, 300, 300, 200, 0, 180);
point(400, 300);
text('JavaScript', 400, 300); JavaScript
(400, 300)
200
(400, 300)
300
200
(400, 300)
300
200
(400, 300)
(500, 500)
(200, 400) (600, 500)
(400, 100)
(400, 300)
(400, 300)
(400, 300)

Practicing graphical instructions
• Exercise 1: On a blank piece of paper
draw an object / scene using only basic
shapes such as circles, lines, rectangles.
Convert that drawing into code!
OR
• Exercise 2: Download the “Draw with
code” booklet from the downloads
section. Choose any drawing, print the
page and type-in the program.
Note: Programs from the “Draw with code” booklet may have more instructions then presented here. Try to discover their purpose.

Introducing variables
let r = 100;
let r2 = 100 - 4;
circle(100, 100, r);
circle(100, 100, r2);
OR
• JavaScript allows users to define variables to hold various values or the result of complex calculations
• You can name variables however you prefer… but don’t start them with number or weird symbols
• Variables are super important in programming

Expressions and variables instead of scalars
circle(100, 100, 100);
circle(100, 100, 96);
You can let the computer do
calculations. At the end of the
day, your computer is also a
powerful calculator.
circle(100, 100, 100);
circle(100, 100, 100 - 4);
let r2 = 100 – 4;
circle(100, 100, 100);
circle(100, 100, r2);

Building our own custom instructions
circle2();
function circle2()
{
circle(100, 100, 100);
circle(100, 100, 100 - 4);
}
• We placed the two circle
instructions inside a code block
(delimited by curly brackets)
• The block is the body of function
circle2. Notice carefully the
syntax.
• The function circle2 is our new
custom instructions. However,
exactly like circle, it doesn’t do
anything until we call it.
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2
3
1
2
3

Functions with parameters
circle2(400, 300, 100);
function circle2(x, y, r)
{
circle(x, y, r);
circle(x, y, r - 4);
}
Now this is a useful
function! It can be used to
draw a double-circle on the
canvas.
We can control the
position and radius of the
double circle!
Exercise: Design your own custom instruction (e.g. function) to draw something useful.

Modularizing code with functions
• Functions can also be used to modularize big pieces of code into smaller pieces
• The smaller pieces can then be assembled or reused exactly like Lego pieces
Exercise: Copy or type-in the “Car” program
from the “Draw with code” booklet /
playground.
If you typed everything correctly you should see
the following drawing when running the
program.

Modularizing the code
function background()
{
// Background
noStroke();
fill(180, 199, 231);
rect(0, 0, 800, 500);
fill(191, 144, 0);
rect(0, 500, 800, 100);
}
function sun()
{
// Sun
fill("yellow");
circle(750, 50, 150);
stroke("yellow");
strokeWeight(6);
line(480, 60, 561, 47);
line(548, 224, 602, 172);
line(740, 304, 747, 236);
}
function car()
{
// Car
stroke("black");
strokeWeight(1);
fill(112, 173, 71);
rect(175, 340, 223, 54);
rect(108, 394, 362, 74);
fill(132,60,12);
circle(168, 468, 32);
circle(408, 468, 32);
}
background();
sun();
car();
This is main body of our new program. Of course, this program calls the
specified functions.
In big programs, functions can be moved outside the main program in
external module or libraries.

Defining loop() function
{
...
}
function sun()
{
...
}
function car()
{
...
}
function loop()
{
background();
sun();
car();
}
• loop() is a special
function.
• We don’t have to
call it.
• The system will call
it automatically
about 60 times /
second.

Parametrize car() function
car(108);
function car(x)
{
// Car
stroke("black");
strokeWeight(1);
fill(112, 173, 71);
rect(x + 67, 340, 223, 54);
rect(x, 394, 362, 74);
fill(132,60,12);
circle(x + 60, 468, 32);
circle(x + 300, 468, 32);
}
We’ll update function car() to
accept a parameter x
representing the x coordinate
where the car will be drawn.

x = 108 x = 400 x = 650
… …
function loop()
{
Step 1: Clear the frame
Step 2: Redraw the
scene and car at
position x
Step 3: Increase
position x by 1
}
Animations

Increasing / decreasing variables
x++;
x += 1;
x = x + 1;
x--;
x -= 1;
x = x - 1;
Increasing the value Decreasing the value
Note: x++ and x-- forms always modify the value by 1.
The other forms can be used to modify the value by an arbitrary amount.
OR
OR
OR
OR

Next steps
• Complete the exercises presented today. Don’t
be frustrated if you’ll encounter errors. Coding
required lots of practice until you get
comfortable writing programs.
• When working on a program, try to run the
program from time to time to avoid
accumulation of errors.
• Explore the other tutorials and projects from
the codeguppy.com website and don’t forget to
visit also the downloads section.
Algorithms More…
Games
Animations

https://codeguppy.com
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Introduction to Coding

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