JavaScript Documentation

Basics

Printing to Console

// Using the console.log() function will print the text
// to the console and create a line break 

console.log("Hello World.");
console.log("How are you?");
// prints:
// Hello World.
// How are you?

// Concatenate strings and variables using the "+" sign

console.log("Greetings " + "Earthling."); 
// prints:
// Greetings Earthling

let species = "Martian";
console.log("Greetings " + species); 
// prints: 
// Greetings Martian
console.log("Greetings " + species + ". Welcome to Earth!");
// prints:
// Greetings Martian. Welcome to Earth!

Variables

// Declare a variable
let myVarName;

// Declare and initialize a variable
let myVarName = 5;

// Assign value to an existing variable
myVarName = 10;

// Print a variable
console.log(myVarName);
console.log("The value is: " + myVarName);

// If a variable isn't going to change its value, it is
// best to use the keyword 'const'

// Variables defined with const:
//   * cannot be redeclared
//   * cannot be reassigned
//   * must be assigned a value when they are declared
 
// Example:
const PI = 3.141592653589793;
PI = 5;      // This will give an error

User Input

// Read a string
// Strings are a series of characters - ex) Hello World
let choice = readLine("What would you like? ");

// Read an integer
// Integers are numbers without a decimal point - ex) 3
let num = readInt("Enter a number: ");

// Read a float
// Float are numbers with a decimal point - ex) 3.14
let cost = readFloat("Enter the cost: ");

// Read a boolean
// Boolean are true/false
let workIsDone = readBoolean("Did you finish your work? ");

Asynchronous User Input

/* In addition to the blocking input methods that receive input via 
popup, there are additional asynchronous input methods. readLineAsync, 
readIntAsync, readFloatAsync, and readBooleanAsync are non-blocking 
functions that can be used in combination with the `await` keyword to 
receive input asynchronously.
*/

let name = await readLineAsync("What's your name? ");
console.log("Nice to meet you, " + name);
        

To read more about asynchronous user input, see this tutorial.

Math

// Operators:
+	Addition
-	Subtraction
*	Multiplication
/	Division
**  Exponentiation
%	Modulus (Remainder)
()	Parentheses (For order of operations)

// Examples
let z = x + y;
let w = x * y;

// Increment (add one)
x++

// Decrement (subtract one)
x--

// Shortcuts
x = x + y;		x += y;
x = x - y;		x -= y;
x = x * y;		x *= y;
x = x / y;		x /= y;

// Exponentiation
let squared = 5 ** 2;
console.log(squared);   // prints out 25

// Modulus
let z = 14 % 4;     // 14 ÷ 4 = 3 with a remainder of 2
console.log(z);     // prints out 2

// Absolute value
let abs = Math.abs(x);

// Square root
let sqrt = Math.sqrt(x);

// Rounding
// Math.round() can be used to round numbers
const PI = 3.14;
let roundedPi = Math.round(PI);
console.log(roundedPi);		// prints out: 3

const GOLDEN_RATIO = 1.618;
let roundedGoldenRatio = Math.round(GOLDEN_RATIO);
console.log(roundedGoldenRatio);		// prints out: 2

// Floor Division
// Math.floor() can be used to perform floor
// division. With floor division, only the
// integer portion of the quotient is returned.

// For example, 5/2 is 2.5, but with floor division,
// the result is 2 and the .5 is discarded.
let result = Math.floor(5/2);
console.log(result);		// prints out: 2


// Geometry
// Note input is in radians, not degrees

Math.sin(radians); // Returns value between -1 and 1
Math.cos(radians); // Returns value between -1 and 1
Math.tan(radians); // Returns value

Random Numbers

// There are several different random methods
Randomizer.nextInt(low, high);
Randomizer.nextBoolean();
Randomizer.nextFloat(low, high);
Randomizer.nextColor();

// Example rolling a dice to get a random roll
let roll = Randomizer.nextInt(1, 6);

Functions

// A function is a reusable block of code that
// performs a specific task when called.

// To call a function, write the function name,
// followed by parentheses:
printGreeting();

// To define what a function does, use the "function"
// keyword and put the task inside the {} brackets:
function printGreeting() {
    console.log("Hi there!");
}

// Functions can take in values, called parameters.

// The function below takes in a parameter called 
// 'name' and prints it in a greeting.
function printGreeting(name) {
    console.log("Hi there " + name);
}

// To call a function that has a parameter, you need
// to include a value, or arguement, when calling it:
printGreeting("Sami");

// Functions can also return a value.

// The function below takes in a value,
// adds two to it, and returns it.
function addTwo(number) {
    return number + 2;
}

Strings

// str.length returns the length of a string

// Example
let str = "hello";
let len = str.length; // equals 5

// str.indexOf(search) returns the first index of the search
// or -1  if not found. It is case sensitive.

//Examples
let str = "hello";
let pos1 = str.indexOf("l"); // returns 2
let pos2 = str.indexOf("H"); // returns -1

// str.substring(start) returns a substring including the
// character at start to the end of the string

//Examples
let str = "hello";
let sub1 = str.substring(1); // equals "ello"
let sub2 = str.substring(3); // equals "lo"

// str.substring(start, end) returns a substring including the
// character at start, but not including the character at end

//Examples
let str = "hello";
let sub1 = str.substring(0,2); // equals "he"
let sub2 = str.substring(1,4); // equals "ell"

To read more about string methods, see this tutorial.

Graphics

CodeHS Library

Check out our full documentation for the CodeHS Graphics Library!

Canvas

// returns the width of the canvas
getWidth();

// returns the height of the canvas
getHeight();

// Example returns the y coordinate of the
// center of the canvas
const CENTER_Y = getHeight() / 2;

// Example returns the x coordinate of the
// center of the canvas
const CENTER_X = getWidth() / 2;

// Removes all objects from the canvas
removeAll();

// Customizes the width and height of the canvas
setSize(width, height);

Circles

// To make a circle
let circle = new Circle(radius);

// To set the location of the center of the circle
circle.setPosition(x, y);

// Example, red circle with 50px radius with center at (100, 200)
let circle = new Circle(50);
circle.setPosition(100, 200);
circle.setColor("red");

// Get the radius
circle.getRadius();					// returns 50
let curRadius = circle.getRadius();	// store in variable

// Change the radius
circle.setRadius(100);

// Get the position of the center of the circle
let x = circle.getX();  // x is 100
let y = circle.getY();  // y is 200

// Change the location of the circle
let x = getWidth() / 2;
let y = getHeight() / 2;
circle.setPosition(x, y);   // circle center is in the center of the screen

// Adding to and removing from screen
add(circle); // Add to screen
remove(circle); // Remove from screen

// Move the circle dx horizontally and dy vertically
circle.move(dx, dy);

Rectangles

// To make a rectangle
let rect = new Rectangle(width, height);

// To set location of the upper left corner of rectangle
rect.setPosition(x, y);

// Example, 200x50 blue rectangle with upper left corner at (100, 200)
let rect = new Rectangle(200, 50);
rect.setPosition(100, 200);
rect.setColor("blue");

// Get location of the upper left corner of the rectangle
let x = rect.getX(); // x is 100
let y = rect.getY(); // y is 200

// Change location of the rectangle
let x = getWidth() / 2;
let y = getHeight() / 2;
rect.setPosition(x, y)  // upper left corner is at center of screen

// Adding to and removing from screen
add(rect); // Add rectangle
remove(rect); // Remove rectangle

// Move the rect dx horizontally and dy vertically
rect.move(dx, dy);

Arcs

// To make an arc
let myArc = new Arc(radius, start, end, unit);

// More specifically, the parameters are:
//    1. radius of the arc
//    2. starting angle of the arc
//    3. ending angle of the arc
//    4. angle unit (0 for degrees, 1 for radians)

// To set the position of the center of the arc
myArc.setPosition(x, y);

// Example, a 90-degree arc with
// radius of 50 and color of red:
let myArc = new Arc(50, 0, 90, 0);
myArc.setPosition(100, 200);
myArc.setColor("red");

// Get the location of the center of the arc
let x = myArc.getX();   // x is 100
let y = myArc.getY();   // y is 200

// Change the location of the center of the arc
let x = getWidth() / 2;
let y = getHeight() / 2;
myArc.setPosition(x, y);    // arc center is at center of screen

// Adding to and removing from screen
add(myArc); // Add arc
remove(myArc); // Remove arc

Lines

// To draw a line from (x1, y1) to (x2, y2)
let line = new Line(x1, y1, x2, y2);

// Set the line color to green
line.setColor("green");

// Set the line width to 10 pixels
line.setLineWidth(10);

// Adding to and removing from screen
add(line);
remove(line);

// Move the line dx horizontally and dy vertically
line.move(dx, dy);

// Change the starting point of the line to (x1, y1)
line.setPosition(x1, y1);

// Change the end point of the line to (x2, y2)
line.setEndpoint(x2, y2);

//Get the starting point of the line
let x = line.getX();    // x has same value as x1
let y = line.getY();    // y has same value as y1

Ovals

// To make an Oval
let oval = new Oval(width, height);

// To set location of the center of the oval
oval.setPosition(x, y);

// Example, 200x50 blue oval with center at (100, 200)
let oval = new Oval(200, 50);
oval.setPosition(100, 200);
oval.setColor("blue");

// Get location of the center of the oval
let x = oval.getX(); // x is 100
let y = oval.getY(); // y is 200

// Change location of the oval
let x = getWidth() / 2;
let y = getHeight() / 2;
oval.setPosition(x, y)  // oval's center is at center of screen

// Adding to and removing from screen
add(oval); // Add oval
remove(oval); // Remove oval

// Move the oval dx horizontally and dy vertically
oval.move(dx, dy);

Polygons

// To make a polygon
let polygon = new Polygon();

// To add points to the polygon
polygon.addPoint(x, y);

// Example, 4-sided green polygon
// NOTE: The order in which you add the points
// determines how the polygon is drawn
let polygon = new Polygon();
polygon.addPoint(20, 20);
polygon.addPoint(10, 50);
polygon.addPoint(100, 80);
polygon.addPoint(60, 10);
polygon.setColor("green");

// Check if polygon contains a point
polygon.containsPoint(x, y); // returns boolean

// Adding to and removing from screen
add(polygon); // Add polygon
remove(polygon); // Remove polygon

// Move the polygon dx horizontally and dy vertically
polygon.move(dx, dy);

Text

// To make a graphical text object
let txt = new Text(label, font);

// To set the position of the lower left corner of the text
txt.setPosition(x, y);

// Example
let txt = new Text("Hello, world!", "30pt Arial");
txt.setPosition(100, 200);
txt.setColor("blue");

// Change what the text says
txt.setText("Goodbye!");

// Get the location of the lower left corner of text
let x = txt.getX(); // x is 100
let y = txt.getY(); // y is 200

// Change the location of the text
let x = getWidth() / 2;
let y = getHeight() / 2;
txt.setPosition(x, y)   // text's lower left corner is
                        // in the center of the screen

// Get the width and height of the text object
let width = txt.getWidth();
let height = txt.getHeight();

// Adding to and removing from screen
add(txt); // Add text
remove(txt); // Remove text

// Move the text dx horizontally and dy vertically
txt.move(dx, dy);

Images

// A web image can be added to the graphics canvas
// as a WebImage. WebImages are created, sized,
// and positioned much like other graphics objects.

// To create a new WebImage, use a URL that links
// directly to the image on the Internet.
// Use the Upload Tab in the editor to upload and create
// a valid URL for your own image.

let copter = new WebImage("https://static.codehs.com/img/library/objects/helicopter.png");

// set the dimensions of the image
copter.setSize(300, 150); 
// set the location of the image
copter.setPosition(getWidth()/4, getHeight()/2); 
// Adding copter to screen
add(copter); 
// Removing copter from screen
remove(copter); 

// Image getter commands return information about your image
// Note that you need to make sure the image is loaded 
// first before you use these commands. The .loaded method
// will call a function once the image is loaded.

// Write a getDimensions function with the getters
copter.loaded(getDimensions); 
// or
copter.loaded(function() {
    // gets the x-coordinate of the image's top left corner
    console.log(copter.getX()); 
    // gets the y-coordinate of the image's top left corner
    console.log(copter.getY()); 
    // gets the width of the image
    console.log(copter.getWidth());
    // gets the height of the image
    console.log(copter.getHeight()); 
});

// Note that the URL to the image must be directly
// to the image file itself. It should generally end with
// something like .png, .jpg, or another image file type.

// To replace the image content of a WebImage, you can call
// .setImage(url):
let animal = new WebImage('https://static.codehs.com/img/library/characters/penguin.png');
add(animal);

animal.setImage('https://static.codehs.com/img/library/characters/monkey.jpg');

CodeHS Image Library

• https://static.codehs.com/img/library/characters/penguin.png
• https://static.codehs.com/img/library/characters/monkey.jpg
• https://static.codehs.com/img/library/characters/leopard.jpg
• https://static.codehs.com/img/library/characters/chameleon.jpg
• https://static.codehs.com/img/library/characters/lizard.jpg
• https://static.codehs.com/img/library/characters/butterfly.jpg
• https://static.codehs.com/img/library/objects/icicle.png
• https://static.codehs.com/img/library/objects/helicopter.png
• https://static.codehs.com/img/library/objects/asteroid.png
• https://static.codehs.com/img/library/objects/soccerBall.png
• https://static.codehs.com/img/library/landscapes/flowers.jpg

Color

You can visit the W3Schools CSS Colors page for a list of colors.

// You can use the setColor() method to give your objects a color
// like this:
obj.setColor(color);

// You can pass in to setColor() any CSS color name as a string.
// Refer to the link above for a list of possible color names

// For example, here is how we set a circle to be teal:
let circle = new Circle(10);
circle.setColor("teal");

// You can also choose your own color by giving a red, green,
// and blue component like
let color = new Color(r, g, b);

// The values are between 0-255 for each component. After making
// a new color, you can use it to set the color of an object.

// For example, to set an existing rectangle called
// rect to be brown:
let brown = new Color(139, 69, 19);
rect.setColor(brown);

// Another way to set the color of an object is to use a
// string with the hexadecimal color value with setColor.
// For example, to set a rect object to be pink:
rect.setColor("#FF66CC");

// There are also many color constants. You can set an objects
// color like this:
obj.setColor(Color.RED);

// List of available color constants:
Color.RED
Color.GREEN
Color.BLUE
Color.YELLOW
Color.CYAN
Color.ORANGE
Color.WHITE
Color.BLACK
Color.GRAY
Color.PURPLE

// Other fun functions

// Return a random color within a group
let color = Color.randomRed();
let color = Color.randomGreen();
let color = Color.randomBlue();

// Get a random color from the randomizer
let color = Randomizer.nextColor();

Rotation

/**
* The following graphic objects can be rotated:
* - Rectangle
* - Arc
* - Line
* - Oval
* - Text
* - WebImage
*/

// Set the rotation of the rectangle with these parameters:
//    1. angle to rotate
//    2. angle unit (0 for degrees, 1 for radians)
//       This will default to degrees.

// Sets rotation of the rectangle to 45 degrees
rect.setRotation(45, 0);           
rect.setRotation(45);       // Does the same thing.

// Sets rotation of the rectangle to Math.PI/2 radians
rect.setRotation(Math.PI / 2, 1);  

// Add rotation with these parameters:
//    1. angle to rotate
//    2. angle unit (0 for degrees, 1 for radians)
//       This will default to degrees.

// Rotates the rectangle by 45 degrees
rect.rotate(45, 0);     
rect.rotate(45);        // Does the same thing.

// Rotates the rectangle by Math.PI/2 radians
rect.rotate(Math.PI / 2, 1);  

Graphics Type and Layers

// To get the type of the object:
let type = obj.getType();

// could return: 'Circle', 'Rectangle', 'Text', 'Line', or 'WebImage'


/* You can change the order of your graphics by
 * using the layer property. Setting the layer
 * to 0 sends the graphic to the very back of the canvas.
 * The graphic with a higher layer number will be
 * drawn on top of objects with a lower layer number.
 * The default layer of a graphic is 1.
 */

obj.layer = 1; // moves the graphic forward to 1 layer
obj2.layer = 5; // will be drawn on top of layers 0 - 4

Debug Mode and Anchors

/* 
 * The debug method can be used to see where 
 * an object's anchor point is located
 * By default, a circle's anchor point is 
 * at its center and a rectangle's anchor point
 * is located at its top-left corner.
 * The debug method evaluates a boolean and can
 * be set to 'true' for any object
 */ 

// The debug method is set to 'false' by default
// Here's how you can turn it on for a circle object:
let circle = new Circle(50);
circle.debug = true;

/*
 * You can also change an object's anchor point
 * by using setAnchor()
    * An anchor of 0, 0 will cause the shape to 
      draw with its position at its top left corner
    * An anchor of 0.5, 0.5 will cause the shape
      to draw with its position at its center
    * An anchor of 1, 1 will cause the shape to
      draw with its position at its bottom right corner
 */
 
// Here's how you can change the anchor point of
// a rectangle to be at the bottom right corner:
let rect = new Rectangle(50, 25);
rect.setAnchor({vertical: 1, horizontal: 1});
 
// Note: it is best to change the anchor point while debug mode is on

Control Structures

Booleans

// A boolean is either true or false
let myBoolean = true;

let anotherBoolean = false;

let result = readBoolean("Question? ");

// Not Operator
let x = !y; 	// x gets the opposite of y

// And Operator
let andExp = x && y;

// Or Operator
let orExp = x || y;

// You can combine many booleans!
let boolExp = x && (y || z);

If Statements, If/Else, If/Else If/Else

if (BOOLEAN_EXPRESSION) {
    // code to execute if the experession is true
}

if (BOOLEAN_EXPRESSION) {
    // code to execute if the expression is true
} else {
    // code to execute if the expression is false
}

if (x < 0) {
    console.log("x is negative.");
}

if (color == "red" || color == "blue" || color == "yellow") {
    console.log("Primary color.");
} else {
    console.log("Not a primary color.");
}

// You can use else if you have multiple
// conditions, but only one should happen.
if (condition_1) {

} else if (condition_2) {

} else if (condition_3) {

} else {

}

// You can always write these using nested
// if/else. For example:
if (condition_1) {
    // code here runs if condition 1 is true
} else {
    if (condition_2) {
        // if condition 2 is true
    } else {
        // and here if condition 2 is false
    }
}

Logical Operators

// Logical operators return booleans (true/false values)
x && y 	// AND operator -- true if BOTH x and y are true
x || y  // OR operator -- true if x OR y are true
! x 	// NOT operator -- true if x is false (and false if x is true)

// Logical operators in if statements
if (x && y) {
    console.log("x and y are both true");
}

if (x || y) {
    console.log("x and/or y are true");
}

if (!x && y) {
    console.log("x is false and y is true");
}

Comparison Operators

// Comparison operators return booleans (true/false values)
x == y 		// is x equal to y
x != y      // is x not equal to y
x > y 		// is x greater than y
x >= y 		// is x greater than or equal to y
x < y 		// is x less than y
x <= y 		// is x less than or equal to y

// Comparison operators in if statements
if (x == y) {
    console.log("x and y are equal");
}

if (x > 5) {
    console.log("x is greater than 5.");
}

For Loops

// for loops repeat code a specific number of times

const COUNT = 5;

for (let i = 0; i < COUNT; i++) {
    /* Repeat code betweeen the brackets 5 times,
     * as the COUNT variable is 5. */
}

// Print numbers 0-9
for (let i = 0; i < 10; i++) {
    console.log(i);
}

While Loops

// while loops repeat until a boolean expression becomes false

while(boolean expression){
    /* Repeat code betweeen brackets while
     * 'boolean expression' is true */
}

// Countdown from from 15 to 10
let i = 15;
while (i > 9) {
    console.log(i);
    i--;
}

// Use a break statement to exit out of a loop
while (true) {
    // code to repeat
    if (condition) {
        break;      // breaks out of while loop
    }
}

Animation

Timers

setTimer(fn, delay); // Create a timer
stopTimer(fn); 		 // Stop a timer

// Example: call moveBall every 40 milliseconds
function main() {
    setTimer(moveBall, 40);
}

function moveBall() {
    ball.move(x, y);
}

main();

Mouse Events

// Mouse events are used to create programs
// that respond to users' mouse clicks, drags,
// and movements.

// When the mouse event occurs, the function
// registered with the event will be called. Note
// that you leave out the parentheses () when
// passing the name of the function.

// Here is a list of mouse events that can be used:
mouseMoveMethod(functionToCall);	// on mouse movement
mouseClickMethod(functionToCall);	// on mouse clicks
mouseDragMethod(functionToCall);	// on mouse drags
mouseDownMethod(functionToCall);	// mouse button depressed
mouseUpMethod(functionToCall);		// mouse button released

// Sample program using mouse events
function main() {
    // Set up mouse callbacks
    mouseMoveMethod(onMouseMove);
    mouseClickMethod(addBall);
    mouseDragMethod(updateLine);
}

function onMouseMove(e) {
    console.log("Mouse is at (" +
            e.getX() + ", " +
            e.getY() + ").");
}

function addBall(e) {
    let ball = new Circle(20);
    ball.setPosition(e.getX(), e.getY());
    add(ball);
}

function updateLine(e) {
    line.setEndpoint(e.getX(), e.getY());
}

main();

// The function getElementAt(x, y) can be used to grab
// an object, if one exists, at the coordinates
// (x, y). If none present, returns null

// Example
function main() {
    mouseClickMethod(turnRed);
}

// If you click on an object, turn it red.
function turnRed(e) {
    let elem = getElementAt(e.getX(), e.getY());
    if (elem != null) {
        elem.setColor("red");
    }
}

main();

Keyboard Events

// Similar to mouse events, you can also capture
// keyboard events


function main() {
    // Set up keyboard callbacks
    keyDownMethod(keyDown);
    keyUpMethod(keyUp);
}

// Current approach is to use e.key to get info about
// which key is pressed
function keyDown(e) {
    if (e.key == "ArrowLeft") {
        ball.move(-5, 0);
    }
    if (e.key == "k"){
        console.log("You pressed k");
    }
    if (e.key == "Enter"){
        console.log("You pressed Enter");
    }
    if (e.key == " "){
        console.log("You pressed Space key");
    }
}

function keyUp(e) {
    console.log("You lifted up a key");
}

main();

Audio Files

// To add a sound file to a program, first create a variable
// to store the sound you want. Be sure to use a link
// directly to the audio file itself (for example,
// if it's an mp3, the link should end with .mp3).
// The link must be a full URL to a sound file that
// is available on the internet.
let mySong = new Audio("link_to_sound_file.mp3");

// To play the file, use .play()
mySong.play();

// To pause a file, use .pause()
mySong.pause();

// To loop a file, first play the file,
// then set .loop to true:
mySong.play()
mySong.loop = true;

Sound

/*
* Create your own sound waves!
*/

// Construct a new Sound with a given note and sound wave type
let sound = new Sound("C4", "square");
let sound2 = new Sound("C1", "sawtooth");

// Set the tone to either a frequency value or a note value
sound.setFrequency(440);   // 440 Hz
sound.setFrequency("C4");  // Middle C note
sound.setFrequency("A2");  // Low A note
sound.setFrequency("A#8");  // High A sharp note

/*
* Set the oscillator type for the sound wave. Options are:
*
* Basic waves: "square", "sine", "triangle", or "sawtooth"
* Fat waves: "fatsquare", "fatsine", "fattriangle", or "fatsawtooth"
* AM waves: "amsquare", "amsine", "amtriangle", or "amsawtooth"
* FM waves: "fmsquare", "fmsine", "fmtriangle", or "fmsawtooth"
* Special waves: "pwm", or "pulse"
* Drum sound: "drum"
* Cymbal sound: "metal"
*/
sound.setOscillatorType("sine");
sound.setOscillatorType("square");

// Set the volume (in decibels)
sound.setVolume(2);

/*
* Get information about the sound
*/

let currentVolume = sound.getVolume();
let currentNote = sound.getFrequency();
let currentOscillatorType = sound.getOscillatorType();


/*
* Adding effects to the sound
* Options are: "distortion", "reverb",
* "tremolo", "vibrato", or "chebyshev"
*/

// Add a distortion effect at full capacity
sound.setEffect("distortion", 1);

// Add a tremolo effect at half capacity
sound.setEffect("tremolo", 0.5);

// Add a vibrato effect at 0 capacity
sound.setEffect("vibrato", 0);


// Starting and stopping the sound

// Play the sound continuously
sound.play();

// Play the sound for 3 seconds
sound.playFor(3);

// Stop playing the sound immediately
sound.stop();

Data Structures

Arrays

// Create an empty array
let arr = [];

// Create an array with values
let arr = [1, 2, 4];

// An array can have any type of data (x is a variable)
let arr = [4, "hello", x];

// Access an element in an array with arr[index];
let firstElem = arr[0];

// Set an element in an array
arr[4] = 9;

// length of an array
let length = arr.length;

// Looping over an array
for (let i = 0; i < arr.length; i++) {
    let element = arr[i];
    // Print out every element and its index
    console.log("Index " + i + ": " + element);
}

// Can also use for...of loops if you don't want the indexes
for (let element of arr) {
    console.log(element);
}

// Add to an array
arr.push(elem);

// Remove last element from array
let last = arr.pop();

// Finding the index of an element
let index = arr.indexOf(5);

// Remove an element at an index i
arr.remove(i)

// Careful, arrays are assigned by reference
let arr1 = [1, 2, 3, 4];
let arr2 = arr1;    // arr2 is now pointing to the same data as arr1
arr2.push(9);       // changing arr2 also changes arr1
console.log(arr1);  // prints [1, 2, 3, 4, 9]

/* ======== Additional array methods ======== */

// Checks to see if a single item is included within an array.
// Returns true if included, false if not included.
array.includes(item)

// Grabs the index of an item within an array. Returns the index
// of the item if in the array, otherwise returns -1.
array.indexOf(item)

// Calls a function for every item in an array (with the item and
// its index as the parameters). This method does NOT alter the
// original array or return anything on its own.
array.forEach(functionName)

// Calls a function for every item in an array (with the item
// as the parameter). This method will return a new array with
// the new items, without changing the original array.
array.map(functionName)

// Calls a function for every item in an array (with the item
// as the parameter). The function itself should return true
// or false depending on whether the item satisfies a defined
// condition. Using this method will return true only if all
// items meet the function condition (ie, the function returns
// true for every item).
array.every(functionName)

// Calls a function for every item in an array (with the item
// as the parameter). The function itself should return true or
// false depending on whether the item satisfies a defined 
// condition. Using this method will return true if at least one
// of the items meets the function condition (ie, the function
// returns true for at least item).
array.some(functionName)

// Starts at the specified index and removes a specific number
// of items from the array. This method returns the removed 
// items in a new array.
array.splice(starting index, # items to remove)

// Starts at the specified index and copies items (up to the
// ending index) into a new array. This method returns a new
// array with the copied items and does NOT affect the original
// array.
array.slice(starting index, ending index)

// returns the items in the array as one string, separated by
// the separator (can be any string). This does NOT affect the
// original array.
array.join(separator)

Objects

// Object literal
let obj = {
    name: "Jeremy",
    color: "blue"
};

// Objects have key-value pairs known as "properties" 

// Set a property with bracket notation
obj["hobby"] = "juggling";

// Set a property with dot notation
obj.faveFood = "french fries";

// Get a property value from a key
let food = obj["faveFood"];   // bracket notation
let food = obj.faveFood;      // dot notation

// Objects can also have key-value actions known as "methods". You
// define them the same way as properties, but the value is
// is a function instead of a single value.
let obj = {
    name: "Jeremy",
    color: "blue",
    greet: function() {
        console.log("Hi there, my name is " + this.name);
    }
};

// In the above object, we use this.name to refer to the name
// property already defined in that object. "this" is a special
// JS keyword that refers to the object itself.

// Adding another method
obj.joke = function() {
    console.log("What do you call a fish with no eyes?");
}

// You call a method with dot notation
obj.greet();    // prints "Hi there, my name is Jeremy"

// Looping over key-value pairs in an object
for (let key in obj) {
    let val = obj[key];
    console.log(key + ": " + val);
    
    // Note that this will include properties and methods. Can use
    // typeof(val) to see if the value is a function (ie method).
    if (typeof(val) != "function) {
        console.log(key + " is a property");
    }
}

// Careful, objects are assigned by reference
let obj1 = {name: "Kate", age:16};
let obj2 = obj1;    // obj2 is now pointing to the same data as obj1
obj2.name = "Sam";  // changing obj2 also changes obj1
console.log(obj1);  // prints {"name":"Sam","age":16}

/* ===== Object Constructors ====== */

// If you're going to be creating multiple copies of certain object,
// like multiple person objects, it's more effective to use an
// object constructor.
function Person(name, color, hobby, food) {
    this.name = name;
    this.color = color;
    this.hobby = hobby;
    this.faveFood = food;
    
    this.greet = function() {
        console.log("Hi there, my name is " + this.name);
    }
}

// An object constructor creates a blueprint to create objects. To
// create a new single object, you call it with the "new" keyword.
let person1 = new Person("Ryan", "blue", "woodworking", "sourdough bread");

person1.greet();    // prints "Hi there, my name is Ryan"
console.log(person1.hobby);     // prints "woodworking"

Sets

// Make a new set named "newSet"
let newSet = new Set();

// Add to a set
newSet.add(5);

// Does a set contain a value
newSet.contains(5); // returns a boolean

// Number of elements in the set
let count = newSet.size; // returns an integer

// Make a new set named "setA"
let setA = new Set();

// Add 2 numbers to the set
setA.add(1);
setA.add(2);

// Make a new set named "setB"
let setB = new Set();

// Add 2 numbers to the set
setB.add(2);
setB.add(3);

// Call the intersect function on "setA" and pass in "setB", store the resulting
// set in a new variable named "mutualSet"
let mutualSet = setA.intersect(setB);

Grids

// Create a grid named "newGrid"
let newGrid = new Grid(rows, cols);

// Get a value in a grid
let elem = newGrid.get(row, col);

// Set a value in a grid
newGrid.set(row, col, val);

// Getting dimensions
let rows = newGrid.numRows();
let cols = newGrid.numCols();

// Is a row, col pair inbounds
newGrid.inBounds(row, col);

// Set all values in grid to initial value
newGrid.init(0); // sets all grid values to 0

// Initialze a grid from an array
newGrid.initFromArray([
    [6, 3, 2],	// 0th row
    [2, 5, 1],	// 1st row
    [4, 3, 9],	// 2nd row
    [1, 5, 1]	// 3rd row
]);