Swift and JavaScript comparison snippets(4) — 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, count: 3)
// threeDoubles is of type [Double], and equals [0.0, 0.0, 0.0]
var anotherThreeDoubles = Array(repeating: 2.5, count: 3)
// anotherThreeDoubles is of type [Double], and equals [2.5, 2.5, 2.5]
var sixDoubles = threeDoubles + anotherThreeDoubles
// sixDoubles is inferred as [Double], 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: Bananas

JavaScript

// creata an empty array
let someInts = new Array()
console.log(`someInts is an array with ${someInts.length} items.`)
// Prints "someInts is an array with 0 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 anotherThreeDoubles = [2.5, 2.5, 2.5]
// anotherThreeDoubles is of type [Double], and equals [2.5, 2.5, 2.5]
let sixDoubles = [...threeDoubles, ...anotherThreeDoubles]
// sixDoubles is inferred as [Double], and equals [0.0, 0.0, 0.0, 2.5, 2.5, 2.5]
// 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: Bananas

Sets

Swift

// Creating and Initializing an Empty Set
var letters = Set()
print("letters is of type Set with (letters.count) items.")
// Prints "letters is of type Set with 0 items."
var favoriteGenres: Set = ["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 hop

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 hop

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"]

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"]

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