JavaScript Documentation
// Using the println() function will print the text and create a line break
// Example of using println()
println("Hello");
println("world.");
// Result:
// Hello
// world.
// Using the print() statement does NOT create a line break
// Example of using print()
print("Hello world. ");
print("How are you?");
// Result:
// Hello world. How are you?
// You can also print to the console using console.log() (includes line break)
// Example:
console.log("Hello world!");
// Declare a variable
var myVarName;
// Initialize a variable
var myVarName = 5;
// Assign to an existing variable
myVarName = 10;
// Print a variable
println(myVarName);
println("The value is: " + myValue);
// Variables can also be declared and initialized using the keyword 'let'
let myVarName;
let myVarname = 5;
// 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
* Variables defined with const cannot be reassigned
* Variables defined with const must be assigned a value when they are declared
*/
// Example:
const PI = 3.141592653589793;
PI = 5; // This will give an error
// Read a string
// Strings are a series of characters - ex: Hello World
var str = readLine(prompt);
// Read an integer
// Integers are numbers without a decimal point - ex: 3
var num = readInt(prompt);
// Read a float
// Float are numbers with a decimal point - ex: 3.14
var cost = readFloat(prompt);
// Read a boolean
// Boolean are true/false
var bool = readBoolean(prompt);
// You should replace the word prompt with
// the question you'd like to ask. For example:
var name = readLine("What is your name? ");
var age = readInt("What is your age? ");
var finishedWork = readBoolean("Is your work done? ");
/* 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.
// Operators:
+ Addition
- Subtraction
* Multiplication
/ Division
** Exponentiation
% Modulus (Remainder)
() Parentheses (For order of operations)
// Examples
var z = x + y;
var 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
var squared = 5 ** 2;
println(squared); // prints out 25
// Modulus
var z = 10 % 4 // 2 * 4 = 8; 10 - 8 = 2
println(z) // prints out: 2
// Absolute value
var abs = Math.abs(x);
// Square root
var sqrt = Math.sqrt(x);
// Rounding
// Math.round() can be used to round numbers
var pi = 3.14;
var roundedPi = Math.round(pi);
println(roundedPi); // prints out: 3
var goldenRatio = 1.618;
var roundedGoldenRatio = Math.round(goldenRatio);
println(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.
var result = Math.floor(5/2);
println(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
// Random integer between low and high
Randomizer.nextInt(low, high);
Randomizer.nextBoolean();
Randomizer.nextFloat(low, high);
Randomizer.nextColor();
var roll = Randomizer.nextInt(1,6);
var color = Randomizer.nextColor();
// str.length
// returns the length of a string
// Example
var str = "hello";
var 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
var str = "hello";
var pos1 = str.indexOf("l"); // returns 2
var pos2 = str.indexOf("H"); // returns -1
// str.substring(start);
// returns a substring including the
// character at start to the end of the
// string
//Examples
var str = "hello";
var sub1 = str.substring(1); // equals "ello"
var 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
var str = "hello";
var sub1 = str.substring(0,2); // equals "he"
var sub2 = str.substring(1,4); // equals "ell"
// Functions can take in values, called parameters.
// The function below takes in a parameter called
// 'input' and prints it.
function printText(input) {
println(input);
}
// 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;
}
// A boolean is either true or false
var myBoolean = true;
var anotherBoolean = false;
var result = readBoolean("Question? ");
// Not Operator
var x = !y; // x gets the opposite of y
// And Operator
var andExp = x && y;
// Or Operator
var orExp = x || y;
// You can combine many booleans!
var boolExp = x && (y || z);
// 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
// Logical operators in if statements
if(x && y){
println("x and y are both true");
}
if(x || y){
println("x and/or y are true");
}
if(!x && y){
println("x is false and y is true");
}
// 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){
println("x and y are equal");
}
if(x > 5){
println("x is greater than 5.");
}
if(BOOLEAN_EXPRESSION){
// code to execute if true
}
if(BOOLEAN_EXPRESSION){
// code if true
} else {
// code if false
}
if(x < 0){
println("x is negative.");
}
if(color == "red" || color == "blue" || color == "yellow"){
println("Primary color.");
} else {
println("Not a primary color.");
}
// You can use else if 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
}
}
var COUNT = 5;
for(var i = 0; i < COUNT; i++){
/* Repeat code betweeen the brackets 5 times,
* as the COUNT variable is 5. */
}
// Print numbers 0-9
for(var i = 0; i < 10; i++){
println(i);
}
while(boolean expression){
/* Repeat code betweeen brackets while
* 'boolean expression' is true */
}
// Countdown from from 15 to 10
var i = 15;
while(i > 9){
println(i);
i--;
}
// This is a loop and a half format
while(true){
// code
if(condition){
break;
}
}
// Create an empty array
var arr = [];
// Create an array with values
var arr = [1, 2, 4];
// An array can have any type
var arr = [4, "hello", x];
// Access an element in an array
var elem = arr[i];
var firstElem = arr[0];
// Set an element in an array
arr[4] = 9;
// Looping over an array
for(var i = 0; i < arr.length; i++){
var cur = arr[i];
// process cur
}
// length of an array
var length = arr.length;
// Add to an array
arr.push(elem);
// Remove last element from array
var last = arr.pop();
// Finding the index of an element in a list
var index = arr.indexOf(5);
// Remove an element from a list at index i
arr.remove(i)
// Object literal
var obj = {
name: "Jeremy",
color: "blue"
};
// Objects/Maps have a collection of key, value pairs
// Set a value
obj["Jeremy"] = "123-4567";
// Get a value for a key
var phone = obj["Jeremy"];
// Loop over an object
for(var key in obj){
var val = obj[key];
// process key and val
}
// Make a new set named "newSet"
var 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
var count = newSet.size; // returns an integer
// Make a new set named "setA"
var setA = new Set();
// Add 2 numbers to the set
setA.add(1);
setA.add(2);
// Make a new set named "setB"
var 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"
var mutualSet = setA.intersect(setB);
// Create a grid named "newGrid"
var newGrid = new Grid(rows, cols);
// Get a value in a grid
var elem = newGrid.get(row, col);
// Set a value in a grid
newGrid.set(row, col, val);
// Getting dimensions
var rows = newGrid.numRows();
var 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
]);
