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Table of content

This table of content is from The swift programming language guide

The Basics

Constants and Variables

Swift

// declare a constant 
let maximumNumberOfLoginAttempts = 10

// declare a variable
var currentLoginAttempt = 0

// declare multiple constants or multiple variables on a single line, separated by commas
var x = 0.0, y = 0.0, z = 0.0Copy the code

JavaScript

// declare a constant const maximumNumberOfLoginAttempts = 10 // declare a variable var currentLoginAttempt = 0 // or let currentLoginAttempt = 0 // declare multiple constants or multiple variables on a single line, Separated by long list var x = 0.0, y = 0.0, z = 0.0Copy the code

Comments

Swift

// This is a comment.

/* This is also a comment
but is written over multiple lines. */
Copy the code

JavaScript

// This is a comment.

/* This is also a comment
but is written over multiple lines. */
Copy the code

Numeric Type Conversion

Swift

Integer and floating-point Conversion let integerPi = Int(PI)Copy the code

JavaScript

Const PI = 3.14159 // Integer and floating-point Conversion const integerPi = parseInt(PI)Copy the code

Booleans

Swift

let orangesAreOrange = true let turnipsAreDelicious = false if turnipsAreDelicious { print("Mmm, tasty turnips!" ) } else { print("Eww, turnips are horrible.") }Copy the code

JavaScript

const orangesAreOrange = true const turnipsAreDelicious = false if (turnipsAreDelicious) { console.log("Mmm, tasty turnips!" ) } else { console.log("Eww, turnips are horrible.") }Copy the code

Error Handling

Swift

func canThrowAnError() throws {
    // this function may or may not throw an error
}
do {
    try canThrowAnError()
    // no error was thrown
} catch {
    // an error was thrown
}
Copy the code

JavaScript

function canThrowAnError() {
    // this function may or may not throw an error
}
try {
    canThrowAnError()
    // no error was thrown
} catch (e) {
    // an error was thrown
}Copy the code

Basic Operators

Assignment Operator

Swift

let b = 10
var a = 5
a = b

// decomposed tuple with multiple values into multiple variables
let (x, y) = (1, 2)
print("x = \(x), y = \(y)") // x = 1, y = 2Copy the code

JavaScript

let b = 10
var a = 5
a = b

// object matching with destructuring assignment
const {x, y} = {x:1, y:2}
console.log(`x = ${x}, y = ${y}`) // x = 1, y = 2
// or array matching with destructuring assignment
const [x, y] = [1, 2]
console.log(`x = ${x}, y = ${y}`) // x = 1, y = 2Copy the code

Arithmetic Operators

Addition (+)
Subtraction (-)
Multiplication (*)
Division (/)

Swift

1 + 2 // equals 1 + 3 // equals 2 + 3 // equals 3 + 3 // equals 3 + 3 // equals 4 + 3 // world"Copy the code

JavaScript

1 + 2 // equals 1 + 3 // equals 2 + 3 // equals 2 + 3 // equals 3 + 3 // equals 3 + 3 // world"Copy the code

Remainder Operator

Swift

9 % 4    // equals 1
-9 % 4   // equals -1Copy the code

JavaScript

9 % 4    // equals 1
-9 % 4   // equals -1Copy the code

Unary Minus/Plus Operator

Swift

let three = 3
let minusThree = -three       // minusThree equals -3
let plusThree = -minusThree   // plusThree equals 3, or "minus minus three"

let minusSix = -6
let alsoMinusSix = +minusSix  // alsoMinusSix equals -6Copy the code

JavaScript

const three = 3
const minusThree = -three       // minusThree equals -3
const plusThree = -minusThree   // plusThree equals 3, or "minus minus three"

const minusSix = -6
const alsoMinusSix = +minusSix  // alsoMinusSix equals -6Copy the code

Compound Assignment Operators

Swift

var a = 1
a += 2 // a is now equal to 3Copy the code

JavaScript

let a = 1
a += 2 // a is now equal to 3Copy the code

Comparison Operators

Equal to (a == b)
Not equal to (a ! = b)
Greater than (a > b)
Less than (a < b)
Greater than or equal to (a >= b)
Less than or equal to (a <= b)
Identity operators, refer to the same object instance (a === b)
Identity operators, not refer to the same object instance (a ! == b)

Swift

1 == 1 // true because 1 is equal to 1 2 ! = 1 // true because 2 is not equal to 1 2 > 1 // true because 2 is greater than 1 1 < 2 // true because 1 is less than 2  1 >= 1 // true because 1 is greater than or equal to 1 2 <= 1 // false because 2 is not less than or equal to 1 let name = "world" if name == "world" { print("hello, world") } else { print("I'm sorry \(name), but I don't recognize you") } // Prints "hello, world", because name is indeed equal to "world". let p1 = Person(); let p2 = Person(); p1 === p2 // false p1 ! == p2 // trueCopy the code

JavaScript

1 == 1 // true because 1 is equal to 1 2 ! = 1 // true because 2 is not equal to 1 2 > 1 // true because 2 is greater than 1 1 < 2 // true because 1 is less than 2  1 >= 1 // true because 1 is greater than or equal to 1 2 <= 1 // false because 2 is not less than or equal to 1 const name = "world" if (name == "world") { console.log("hello, world") } else { console.log(`I'm sorry ${name}, but I don't recognize you`) } // Prints "hello, world", because name is indeed equal to "world". const p1 = new Person(); const p2 = new Person(); p1 === p2 // false p1 ! == p2 // trueCopy the code

Ternary Conditional Operator

Swift

let contentHeight = 40
let hasHeader = true
let rowHeight = contentHeight + (hasHeader ? 50 : 20)
// rowHeight is equal to 90Copy the code

JavaScript

const contentHeight = 40
const hasHeader = true
const rowHeight = contentHeight + (hasHeader ? 50 : 20)
// rowHeight is equal to 90Copy the code

Logical Operators

Logical NOT (! a)
Logical AND (a && b)
Logical OR (a || b)

Swift

let allowedEntry = false if ! allowedEntry { print("ACCESS DENIED") } // Prints "ACCESS DENIED" let hasDoorKey = false let knowsOverridePassword = true let hasDoorKey = false let knowsOverridePassword = true if enteredDoorCode && passedRetinaScan || hasDoorKey || knowsOverridePassword { print("Welcome!" ) } else { print("ACCESS DENIED") } // Prints "Welcome!"Copy the code

JavaScript

const allowedEntry = false if (! allowedEntry) { console.log("ACCESS DENIED") } // Prints "ACCESS DENIED" const hasDoorKey = false const knowsOverridePassword = true const hasDoorKey = false const knowsOverridePassword = true if (enteredDoorCode && passedRetinaScan || hasDoorKey || knowsOverridePassword) { console.log("Welcome!" ) } else { console.log("ACCESS DENIED") } // Prints "Welcome!"Copy the code

Strings and Characters

String Literals

Swift

let someString = "Some string literal value" // Multiline String Literals with three double quotation marks (""") let quotation = """ The White Rabbit put on his spectacles. "Where shall I begin, please your Majesty?" he asked. "Begin at the beginning," the King said gravely, "and go on till you come to the end; then stop." """ // String Mutability var variableString = "Horse" variableString += " and carriage" // variableString is  now "Horse and carriage" let constantString = "Highlander" constantString += " and another Highlander" // this reports a compile-time error - a constant string cannot be modifiedCopy the code

JavaScript

const someString = "Some string literal value" // Multiline String Literals back-tick (` `) const quotation = ` The White Rabbit put on his spectacles. "Where shall I begin, please your Majesty?" he asked. "Begin at the beginning," the King said gravely, "and go on till you come to the end; then stop." ` // String Mutability let variableString = "Horse" variableString += " and carriage" // variableString is now "Horse and carriage" const constantString = "Highlander" constantString += " and another Highlander" // this reports  a compile-time error - a constant string cannot be modifiedCopy the code

String Interpolation

Swift

// insert values into the string literal is wrapped in a pair of parentheses, Multipliers = "multipliers (\) times 2.5 is \(multiplier) * 2.5)" // Message is "3 times 2.5 is 7.5"Copy the code

JavaScript

Multiplier = 3 const message = '${multiplier} times 2.5 is ${multiplier * 2.5}' // message is "7 times 2.5 is 7.5"Copy the code

Accessing and Modifying a String

Swift

// String Indices let greeting = "Guten Tag!" greeting[greeting.startIndex] // G greeting[greeting.index(before: greeting.endIndex)] // ! greeting[greeting.index(after: greeting.startIndex)] // u // Inserting and Removing var welcome = "hello" welcome.insert("!" , at: welcome.endIndex) // welcome now equals "hello!" welcome.insert(contentsOf: " there", at: welcome.index(before: welcome.endIndex)) // welcome now equals "hello there!" welcome.remove(at: welcome.index(before: welcome.endIndex)) // welcome now equals "hello there" let range = welcome.index(welcome.endIndex, offsetBy: -6).. <welcome.endIndex welcome.removeSubrange(range) // welcome now equals "hello"Copy the code

JavaScript

const greeting = "Guten Tag!"
greeting.slice(0, 1)
// G
greeting.slice(-1)
// !
greeting.substr(1, 1)
// u

// Inserting and Removing
let welcome = "hello"
welcome += "!"
// welcome now equals "hello!"

welcome = welcome.substr(0, welcome.length - 1) + " there" + welcome.slice(-1)
// welcome now equals "hello there!"

welcome.substr(0, welcome.length - 1)
// welcome now equals "hello there"

let index = welcome.indexOf(' ');
welcome.slice(0, index)
// welcome now equals "hello"Copy the code

Collection Types

Mutability of Collections: Arrays

Swift

// creata an empty array var someInts = [Int]() print("someInts is of type [Int] with \(someInts.count) items.") // Prints "someInts is of type [Int] with 0 items." // Creating an Array with a Default Value var threeDoubles = Array (repeating: 0.0, the count: 3) // threeDoubles is of Type [Double], and equals [0.0, 0.0, 0.0] var anotherThreeDoubles = Array(repeating: 2.5, the count: 3) // anotherThreeDoubles is of type [Double], and equals [2.5, 2.5, Var sixDoubles = threeDoubles + anotherThreeDoubles // sixDoubles is equal as [doubles], and equals [0.0, 0.0, 0.0, 2.5, 2.5, 2.5] // Creating an Array with an Array Literal var shoppingList: [String] = ["Eggs", "Milk"] // shoppingList has been initialized with two initial items // Accessing and Modifying an Array if shoppingList.isEmpty { print("The shopping list is empty.") } else { print("The shopping list is not empty.") } // Prints "The shopping list is not empty." shoppingList.append("Flour") // shoppingList now contains 3 items, and someone is making pancakes shoppingList += ["Baking Powder"] // shoppingList now contains 4 items shoppingList += ["Chocolate Spread", "Cheese", "Butter"] // shoppingList now contains 7 items var firstItem = shoppingList[0] // firstItem is equal to "Eggs" shoppingList[0] = "Six eggs" // the first item in the list is now equal to "Six eggs" rather than "Eggs" shoppingList[4...6] = ["Bananas", "Apples"] // shoppingList now contains 6 items shoppingList.insert("Maple Syrup", at: 0) // shoppingList now contains 7 items // "Maple Syrup" is now the first item in the list let mapleSyrup = shoppingList.remove(at: 0) // the item that was at index 0 has just been removed // shoppingList now contains 6 items, and no Maple Syrup // the mapleSyrup constant is now equal to the removed "Maple Syrup" string let apples = shoppingList.removeLast() // the last item in the array has just been removed // shoppingList now contains 5 items, and no apples // the apples constant is now equal to the removed "Apples" string // Iterating Over an Array for item in shoppingList { print(item) } // Six eggs // Milk // Flour // Baking Powder // Bananas for (index, value) in shoppingList.enumerated() { print("Item \(index + 1): \(value)") } // Item 1: Six eggs // Item 2: Milk // Item 3: Flour // Item 4: Baking Powder // Item 5: BananasCopy the code

JavaScript

// creata an empty array let someInts = new Array() console.log(`someInts is an array with ${someInts.length} items.`) // Creating an array with a Default Value let threeDoubles = [0.0, 0.0, 0.0] // threeDoubles is of type [Double], and equals [0.0, 0.0, 0.0] let otherthreedoubles = [2.5, 2.5, 2.5] // anotherThreeDoubles is of type [Double], and equals [2.5, 2.5, 2.5] let sixDoubles = [...threeDoubles, // sixDoubles is mans as [Double], and equals [0.0, 0.0, 0.0, 2.5, 2.5, 2.35] // Creating an Array with an Array Literal let shoppingList = ["Eggs", "Milk"] // shoppingList has been initialized with two initial items // Accessing and Modifying an Array if (shoppingList.length === 0) { console.log("The shopping list is empty.") } else { console.log("The shopping list is not empty.") } // Prints "The shopping list is not empty." shoppingList.push("Flour") // shoppingList now contains 3 items, and someone is making pancakes shoppingList = shoppingList.concat(["Baking Powder"]) // shoppingList now contains 4 items shoppingList = [...shoppingList, "Chocolate Spread", "Cheese", "Butter"] // shoppingList now contains 7 items let firstItem = shoppingList[0] // firstItem is equal to "Eggs" shoppingList[0] = "Six eggs" // the first item in the list is now equal to "Six eggs" rather than "Eggs" shoppingList.splice(4, 3, "Bananas", "Apples") // shoppingList now contains 6 items shoppingList.unshift("Maple Syrup") // shoppingList now contains 7 items // "Maple Syrup" is now the first item in the list let mapleSyrup = shoppingList.shift() // the item that was at index 0  has just been removed // shoppingList now contains 6 items, and no Maple Syrup // the mapleSyrup constant is now equal to the removed "Maple Syrup" string let apples = shoppingList.pop() // the last item in the array has just been removed // shoppingList now contains 5 items, and no apples // the apples constant is now equal to the removed "Apples" string // Iterating Over an Array shoppingList.forEach((item => { console.log(item) }) // Six eggs // Milk // Flour // Baking Powder // Bananas shoppingList.forEach(((item, index) => { console.log(`Item ${index + 1}: ${value}`) }) // Item 1: Six eggs // Item 2: Milk // Item 3: Flour // Item 4: Baking Powder // Item 5: BananasCopy the code

Sets

Swift

// Creating and Initializing an Empty Set var letters = Set<Character>() print("letters is of type Set<Character> with \(letters.count) items.") // Prints "letters is of type Set<Character> with 0 items." var favoriteGenres: Set<String> = ["Rock", "Classical", "Hip hop"] // favoriteGenres has been initialized with three initial items // Accessing and Modifying a Set print("I have \(favoriteGenres.count) favorite music genres.") // Prints "I have 3 favorite music genres." if favoriteGenres.isEmpty { print("As far as music goes, I'm not picky.") } else { print("I have particular music preferences.") } // Prints "I have particular music preferences." favoriteGenres.insert("Jazz") // favoriteGenres now contains 4 items if let removedGenre = favoriteGenres.remove("Rock") { print("\(removedGenre)? I'm over it.") } else { print("I never much cared for that.") } // Prints "Rock? I'm over it." if favoriteGenres.contains("Funk") { print("I get up on the good foot.") } else { print("It's too funky in  here.") } // Prints "It's too funky in here." // Iterating Over a Set for genre in favoriteGenres { print("\(genre)") }  // Classical // Jazz // Hip hopCopy the code

JavaScript

// Creating and Initializing an Empty Set let letters = new Set() console.log(`letters is of type Set with ${letters.size} items.`) // Prints "letters is of type Set with 0 items." let favoriteGenres = new set(["Rock", "Classical", "Hip hop"]) // favoriteGenres has been initialized with three initial items // Accessing and Modifying a Set console.log(`I have ${favoriteGenres.size} favorite music genres.`) // Prints "I have 3 favorite music genres." if (favoriteGenres.size == 0) { console.log("As far as music goes, I'm not picky.") } else { console.log("I have particular music preferences.") } // Prints "I have particular music preferences." favoriteGenres.add("Jazz") // favoriteGenres now contains 4 items const removedGenre = favoriteGenres.delete("Rock") if (removedGenre) { console.log(`${removedGenre}? I'm over it.`) } else { console.log("I never much cared for that.") } // Prints "Rock? I'm over it." if (favoriteGenres.has("Funk")) { console.log("I get up on  the good foot.") } else { console.log("It's too funky in here.") } // Prints "It's too funky in here." // Iterating Over a Set favoriteGenres.forEach(genre => { console.log(genre); }) // Classical // Jazz // Hip hopCopy the code

Dictionaries

Swift

// Creating an Empty Dictionary
var namesOfIntegers = [Int: String]()
// namesOfIntegers is an empty [Int: String] dictionary
namesOfIntegers[16] = "sixteen"
// namesOfIntegers now contains 1 key-value pair
namesOfIntegers = [:]
// namesOfIntegers is once again an empty dictionary of type [Int: String]


// Creating a Dictionary with a Dictionary Literal
var airports: [String: String] = ["YYZ": "Toronto Pearson", "DUB": "Dublin"]


// Accessing and Modifying a Dictionary
print("The airports dictionary contains \(airports.count) items.")
// Prints "The airports dictionary contains 2 items."

if airports.isEmpty {
    print("The airports dictionary is empty.")
} else {
    print("The airports dictionary is not empty.")
}
// Prints "The airports dictionary is not empty."

airports["LHR"] = "London"
// the airports dictionary now contains 3 items

airports["LHR"] = "London Heathrow"
// the value for "LHR" has been changed to "London Heathrow"

if let oldValue = airports.updateValue("Dublin Airport", forKey: "DUB") {
    print("The old value for DUB was \(oldValue).")
}
// Prints "The old value for DUB was Dublin."

if let airportName = airports["DUB"] {
    print("The name of the airport is \(airportName).")
} else {
    print("That airport is not in the airports dictionary.")
}
// Prints "The name of the airport is Dublin Airport."

airports["APL"] = "Apple International"
// "Apple International" is not the real airport for APL, so delete it
airports["APL"] = nil
// APL has now been removed from the dictionary

if let removedValue = airports.removeValue(forKey: "DUB") {
    print("The removed airport's name is \(removedValue).")
} else {
    print("The airports dictionary does not contain a value for DUB.")
}
// Prints "The removed airport's name is Dublin Airport."


// Iterating Over a Dictionary
for (airportCode, airportName) in airports {
    print("\(airportCode): \(airportName)")
}
// YYZ: Toronto Pearson
// LHR: London Heathrow

for airportCode in airports.keys {
    print("Airport code: \(airportCode)")
}
// Airport code: YYZ
// Airport code: LHR

for airportName in airports.values {
    print("Airport name: \(airportName)")
}
// Airport name: Toronto Pearson
// Airport name: London Heathrow

let airportCodes = [String](airports.keys)
// airportCodes is ["YYZ", "LHR"]

let airportNames = [String](airports.values)
// airportNames is ["Toronto Pearson", "London Heathrow"]Copy the code

JavaScript

// Creating an Empty Dictionary let namesOfIntegers = {} // namesOfIntegers is an empty dictionary namesOfIntegers[16] =  "sixteen" // namesOfIntegers now contains 1 key-value pair namesOfIntegers = {} // namesOfIntegers is once again an empty dictionary of type // Creating a Dictionary with a Dictionary Literal let airports = {"YYZ": "Toronto Pearson", "DUB": "Dublin"} // Accessing and Modifying a Dictionary console.log(`The airports dictionary contains ${Object.keys(airports).length} items.`) // Prints "The airports dictionary contains 2 items." if (Object.keys(airports).length == 0) { console.log("The airports dictionary is empty.") } else { console.log("The airports dictionary is not empty.") } // Prints "The airports dictionary is not empty." airports["LHR"] = "London" // the airports dictionary now contains 3 items airports["LHR"] = "London Heathrow" // the value for "LHR" has been changed  to "London Heathrow" const oldValue = airports["DUB"] airports["DUB"] = "Dublin Airport" if (oldValue) { console.log(`The old value for DUB was ${oldValue}.`) } // Prints "The old value for DUB was Dublin." const airportName = airports["DUB"] if (airportName) { console.log(`The name of the airport is ${airportName}.`) } else { console.log("That airport is not in the airports dictionary.") } // Prints "The name of the airport is Dublin Airport." airports["APL"] = "Apple International" // "Apple International" is not the real airport for APL, so delete it airports["APL"] = null delete airports["APL"] // APL has now been removed from the dictionary // Iterating Over a Dictionary Object.keys(airports).forEach(airportCode => { const airportName = airports[airportCode] console.log(`${airportCode}: ${airportName}`) }) // YYZ: Toronto Pearson // LHR: London Heathrow let airportCodes = Object.keys(airports) // airportCodes is ["YYZ", "LHR"]Copy the code

Control Flow

For-In Loops

Swift

let names = ["Anna", "Alex", "Brian", "Jack"] for name in names { print("Hello, \(name)!" ) } // Hello, Anna! // Hello, Alex! // Hello, Brian! // Hello, Jack! let numberOfLegs = ["spider": 8, "ant": 6, "cat": 4] for (animalName, legCount) in numberOfLegs { print("\(animalName)s have \(legCount) legs") } // ants have 6 legs // cats have 4 legs // spiders have 8 legsCopy the code

JavaScript

const names = ["Anna", "Alex", "Brian", "Jack"] for (let i = 0; i < names.length; i++) { console.log(`Hello, ${names[i]}! `) } // Hello, Anna! // Hello, Alex! // Hello, Brian! // Hello, Jack! const numberOfLegs = {"spider": 8, "ant": 6, "cat": 4} Object.keys(numberOfLegs).forEach(animalName => { const legCount = numberOfLegs[animalName]; console.log(`${animalName}s have ${legCount} legs`) }) // ants have 6 legs // cats have 4 legs // spiders have 8 legsCopy the code

While Loops

Swift

let finalSquare = 25 var board = [Int](repeating: 0, count: finalSquare + 1) board[03] = +08; board[06] = +11; board[09] = +09; board[10] = +02 board[14] = -10; board[19] = -11; board[22] = -02; board[24] = -08 var square = 0 var diceRoll = 0 while square < finalSquare { // roll the dice diceRoll += 1 if diceRoll == 7 { diceRoll = 1 } // move by the rolled amount square += diceRoll if square < board.count { // if we're still on the  board, move up or down for a snake or a ladder square += board[square] } } print("Game over!" )Copy the code

JavaScript

let finalSquare = 25 let board = [] for (let i = 0; i < finalSquare.length; i++) { board[i] = 0; } board[03] = +08; board[06] = +11; board[09] = +09; board[10] = +02 board[14] = -10; board[19] = -11; board[22] = -02; board[24] = -08 let square = 0 let diceRoll = 0 while (square < finalSquare) { // roll the dice diceRoll += 1 if (diceRoll == 7) { diceRoll = 1 } // move by the rolled amount square += diceRoll if (square < board.length) { // if we're still on the board, move up or down for a snake or a ladder square += board[square] } } console.log("Game over!" )Copy the code

Conditional Statements

Swift

var temperatureInFahrenheit = 30
temperatureInFahrenheit = 90
if temperatureInFahrenheit <= 32 {
    print("It's very cold. Consider wearing a scarf.")
} else if temperatureInFahrenheit >= 86 {
    print("It's really warm. Don't forget to wear sunscreen.")
} else {
    print("It's not that cold. Wear a t-shirt.")
}
// Prints "It's really warm. Don't forget to wear sunscreen."Copy the code

JavaScript

let temperatureInFahrenheit = 30
temperatureInFahrenheit = 90
if (temperatureInFahrenheit <= 32) {
    console.log("It's very cold. Consider wearing a scarf.")
} else if (temperatureInFahrenheit >= 86) {
    console.log("It's really warm. Don't forget to wear sunscreen.")
} else {
    console.log("It's not that cold. Wear a t-shirt.")
}
// Prints "It's really warm. Don't forget to wear sunscreen."Copy the code

Switch

Swift

let someCharacter: Character = "z"
switch someCharacter {
case "a":
    print("The first letter of the alphabet")
case "z":
    print("The last letter of the alphabet")
default:
    print("Some other character")
}
// Prints "The last letter of the alphabet"Copy the code

JavaScript

const someCharacter = "z"
switch (someCharacter) {
case "a":
    console.log("The first letter of the alphabet")
    break;
case "z":
    console.log("The last letter of the alphabet")
    break;
default:
    console.log("Some other character")
}
// Prints "The last letter of the alphabet"Copy the code

Functions

Swift

// Defining and Calling Functions func greet(person: String) -> String { let greeting = "Hello, " + person + "!" return greeting } print(greet(person: "Anna")) // Prints "Hello, Anna!" print(greet(person: "Brian")) // Prints "Hello, Brian!" func greetAgain(person: String) -> String { return "Hello again, " + person + "!" } print(greetAgain(person: "Anna")) // Prints "Hello again, Anna!" // Function Parameters and Return Values // Functions Without Parameters func sayHelloWorld() -> String { return "hello,  world" } print(sayHelloWorld()) // Prints "hello, world" // Functions With Multiple Parameters func greet(person: String, alreadyGreeted: Bool) -> String { if alreadyGreeted { return greetAgain(person: person) } else { return greet(person: person) } } print(greet(person: "Tim", alreadyGreeted: true)) // Prints "Hello again, Tim!" // Functions Without Return Values func greet(person: String) { print("Hello, \(person)!" ) } greet(person: "Dave") // Prints "Hello, Dave!" // Functions with Multiple Return Values func minMax(array: [Int]) -> (min: Int, max: Int) { var currentMin = array[0] var currentMax = array[0] for value in array[1..<array.count] { if value < currentMin {  currentMin = value } else if value > currentMax { currentMax = value } } return (currentMin, currentMax) } let bounds = minMax(array: [8, -6, 2, 109, 3, 71]) print("min is \(bounds.min) and max is \(bounds.max)") // Prints "min is -6 and max is 109" // Nested Functions func chooseStepFunction(backward: Bool) -> (Int) -> Int { func stepForward(input: Int) -> Int { return input + 1 } func stepBackward(input: Int) -> Int { return input - 1 } return backward ? stepBackward : stepForward } var currentValue = -4 let moveNearerToZero = chooseStepFunction(backward: currentValue > 0) // moveNearerToZero now refers to the nested stepForward() function while currentValue ! = 0 { print("\(currentValue)... ") currentValue = moveNearerToZero(currentValue) } print("zero!" ) / / - 4... / / - 3... / / - 2... / / - 1... // zero!Copy the code

JavaScript

// Defining and Calling Functions function greet(person) { const greeting = "Hello, " + person + "!" return greeting } console.log(greet("Anna")) // Prints "Hello, Anna!" console.log(greet("Brian")) // Prints "Hello, Brian!" function greetAgain(person) { return "Hello again, " + person + "!" } print(greetAgain("Anna")) // Prints "Hello again, Anna!" // Function Parameters and Return Values // Functions Without Parameters function sayHelloWorld() { return "hello, world" } console.log(sayHelloWorld()) // Prints "hello, world" // Functions With Multiple Parameters function greet(person, alreadyGreeted) { if (alreadyGreeted) { return greetAgain(person) } else { return greet(person) } } console.log(greet("Tim", true)) // Prints "Hello again, Tim!" // Functions Without Return Values function greet(person) { console.log(`Hello, ${person}! `) } greet("Dave") // Prints "Hello, Dave!" // Functions with Multiple Return Values function minMax(array) { let currentMin = array[0] let currentMax = array[0] array.forEach(value => { if (value < currentMin) { currentMin = value } else if (value > currentMax) { currentMax = value } }) return {currentMin, currentMax} } const bounds = minMax([8, -6, 2, 109, 3, 71]) console.log(`min is ${bounds.min} and max is ${bounds.max}`) // Prints "min is -6 and max is 109" // Nested Functions function chooseStepFunction(backward) { function stepForward(input) { return input + 1 } function stepBackward(input) { return input - 1 } return backward ? stepBackward : stepForward } const currentValue = -4 const moveNearerToZero = chooseStepFunction(currentValue > 0) // moveNearerToZero now refers to the nested stepForward() function while (currentValue ! = 0) { console.log(`${currentValue}... `) currentValue = moveNearerToZero(currentValue) } console.log("zero!" ) / / - 4... / / - 3... / / - 2... / / - 1... // zero!Copy the code

Closures

Swift

// Closure Expressions
// The Sorted Method
let names = ["Chris", "Alex", "Ewa", "Barry", "Daniella"]
func backward(_ s1: String, _ s2: String) -> Bool {
    return s1 > s2
}
var reversedNames = names.sorted(by: backward)
// reversedNames is equal to ["Ewa", "Daniella", "Chris", "Barry", "Alex"]
reversedNames = names.sorted(by: { (s1: String, s2: String) -> Bool in
    return s1 > s2
})
// or
reversedNames = names.sorted(by: { (s1: String, s2: String) -> Bool in return s1 > s2 } )Copy the code

JavaScript

// Closure Expressions
// The Sort Method
const names = ["Chris", "Alex", "Ewa", "Barry", "Daniella"]
function backward(s1, s2) {
    return s1 < s2
}
let reversedNames = names.sort(backward)
// reversedNames is equal to ["Ewa", "Daniella", "Chris", "Barry", "Alex"]
reversedNames = names.sort((s1, s2) => {
    return s1 < s2
})
// or
reversedNames = names.sort((s1, s2) => return s1 < s2)Copy the code

Classes

Swift

// class definition
class Counter {
    var count = 0
    func increment() {
        count += 1
    }
    func increment(by amount: Int) {
        count += amount
    }
    func reset() {
        count = 0
    }
}

// class instance
let counter = Counter()
// the initial count value is 0
counter.increment()
// the count's value is now 1
counter.increment(by: 5)
// the count's value is now 6
counter.reset()
// the count's value is now 0

print("The count property value is \(counter.count)")
Copy the code

JavaScript

// class definition
class Counter {
    contructor() {
        this.count = 0
    }
    function increment() {
        this.count += 1
    }
    function increment(amount) {
        this.count += amount
    }
    function reset() {
        this.count = 0
    }
}

// class instance
let counter = Counter()
// the initial count value is 0
counter.increment()
// the count's value is now 1
counter.increment(5)
// the count's value is now 6
counter.reset()
// the count's value is now 0

console.log(`The count property value is ${counter.count}`)Copy the code

Inheritance

Swift

Defining a Base Class Class Vehicle {var currentSpeed = 0.0 var description: String { return "traveling at \(currentSpeed) miles per hour" } func makeNoise() { // do nothing - an arbitrary vehicle doesn't necessarily make a noise } } let someVehicle = Vehicle() print("Vehicle: \(someVehicle. Description)") // Vehicle: traveling at 0.0 miles per hour // Subclassing class SomeSubclass: SomeSuperclass { // subclass definition goes here } class Bicycle: Vehicle {var hasBasket = false} let bicycle = bicycle () bicycle. HasBasket = true bicycle. CurrentSpeed = 15.0 print("Bicycle: \(bicycle.description)") // Bicycle: Traveling at 15.0 miles per hour // Subclasses can themselves be subclassed class Tandem: Bicycle { var currentNumberOfPassengers = 0 } let tandem = Tandem() tandem.hasBasket = true Tandem. CurrentNumberOfPassengers = 2 tandem. CurrentSpeed = 22.0 print (" tandem: \ (tandem. The description)) / / tandem: Traveling at 22.0 Miles per hour // Primary Class Train: Vehicle { override func makeNoise() { print("Choo Choo") } } let train = Train() train.makeNoise() // Prints "Choo Choo"  // Overriding Property Getters and Setters class Car: Vehicle { var gear = 1 override var description: String {return super.description + "in gear \(gear)"}} let car = car () car.currentSpeed = 25.0 car.gear = 3 Print ("Car: \(Car. Description)") // Car: traveling at 25.0 miles per hour in gear 3Copy the code

JavaScript

// Defining a Base Class Class Vehicle {constructor() {this.currentSpeed = 0.0} get description() {return 'traveling  at ${currentSpeed} miles per hour` } function makeNoise() { // do nothing - an arbitrary vehicle doesn't necessarily make a noise } } let someVehicle = Vehicle() console.log(`Vehicle: ${someVehicle.description}`) // Vehicle: Traveling at 0.0 miles per hour // Subclassing Class SomeSubclass extends SomeSuperclass {contructor() {super(); } // subclass definition goes here } class Bicycle extends Vehicle { contructor() { super(); This.hasbasket = false}} let bicycle = bicycle () bicycle. HasBasket = true bicycle. CurrentSpeed = 15.0 console.log(`Bicycle: ${bicycle.description}`) // Bicycle: Traveling at 15.0 miles per hour // Subclasses can themselves be subclassed class Tandem extends Bicycle {contructor() { super(); this.currentNumberOfPassengers = 0 } } let tandem = Tandem() tandem.hasBasket = true tandem.currentNumberOfPassengers = 2 tandem.currentSpeed = 22.0 console.log(" tandem: \(tandem.description)") // tandem: Traveling at 22.0 miles per hour // Tpo41 Class Train extends Vehicle {contructor() {super(); this.currentNumberOfPassengers = 0 } function makeNoise() { console.log("Choo Choo") } } let train = Train() train.makeNoise() // Prints "Choo Choo" // Overriding Property Getters and Setters class Car extends Vehicle { contructor() { super(); this.gear = 1 } get description() { return `${super.description} in gear ${gear}` } } let car = Car() car.currentSpeed = 25.0 car.gear = 3 console.log(' car: ${car.description} ') // Car: traveling at 25.0 miles per hour in gear 3Copy the code

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Swift and JavaScript code snippets are relatively simple

Table of content

The Basics

Constants and Variables

Comments

Numeric Type Conversion

Booleans

Error Handling

Basic Operators

Assignment Operator

Arithmetic Operators

Remainder Operator

Unary Minus/Plus Operator

Compound Assignment Operators

Comparison Operators

Ternary Conditional Operator

Logical Operators

Strings and Characters

String Literals

String Interpolation

Accessing and Modifying a String

Collection Types

Mutability of Collections: Arrays

Sets

Dictionaries

Control Flow

For-In Loops

While Loops

Conditional Statements

Switch

Functions

Closures

Classes

Inheritance

Swift and JavaScript code snippets are relatively simple

Table of content

The Basics

Comments

Booleans

Basic Operators

Arithmetic Operators

Unary Minus/Plus Operator

Comparison Operators

Logical Operators

String Literals

Accessing and Modifying a String

Mutability of Collections: Arrays

Dictionaries

For-In Loops

Conditional Statements

Functions

Classes

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