Swift for JavaScript Developers

Variables

let num = 1
console.log(num) // 1
num = 2
console.log(num) // 2

var num = 1
print(num) // 1
num = 2
print(num) // 2

Constants

const num = 1
console.log(num) // 1

let num = 1
print(num) // 1

Strings

const name = "Ali"
const signature = `
  Signed by ${name}
`
console.log(name.length) // 3
console.log(name.toUpperCase()) // "ALI"
console.log(name.startsWith("Al")) // true
console.log(name.endsWith("li")) // true

console.log("x + " + 1) // "x + 1"
console.log(`2 + 2 = ${2 + 2}`) // "2 + 2 = 4"

let name = "Ali"
let signature = """
  Signed by \(name)
"""
print(name.count) // 3
print(name.uppercased()) // "ALI"
print(name.hasPrefix("Al")) // true
print(name.hasSuffix("li")) // true

print("x + " + String(1)) // x + 1
print("2 + 2 = \(2 + 2)") // 2 + 2 = 4

Numbers

let num = 1_000
num += 1
console.log(num) // 1001

Number.prototype.isMultiple = function({ of = 1 }) {
  return this % of === 0
}
console.log(num.isMultiple({ of: 2 })) // false
console.log(4..isMultiple({ of: 2 })) // true

var num = 1_000
num += 1
print(num) // 1001
print(num.isMultiple(of: 2)) // false
print(4.isMultiple(of: 2)) // true

Decimal Numbers

const num = 0.1 + 0.2
console.log(num) // 0.30000000000000004

let x = 1.5
const y = 2
console.log(x + y) // 3.5
console.log(Math.floor(x) + y) // 3

x *= 2
console.log(x) // 3

let num = 0.1 + 0.2
print(num) // 0.30000000000000004

var x = 1.5
let y = 2
print(x + Double(y)) // 3.5
print(Int(x) + y) // 3

x *= 2
print(x) // 3.0

Booleans

let isAdmin = false
isAdmin = !isAdmin
console.log(isAdmin) // true

var isAdmin = false
isAdmin = !isAdmin
print(isAdmin) // true

isAdmin.toggle()
print(isAdmin) // false

Arrays

const numbers = [1, 2, 3]
numbers.push(4)

const names = new Array()
names.push("Ali")
console.log(names[0]) // "Ali"

const grades = []
grades.push(73)

let alphabet = ["a", "b", "c", "d"]
console.log(alphabet.length) // 4
console.log(alphabet.splice(2, 1)) // ["c"]
alphabet.length = 0

alphabet = ["c", "a", "d", "b"]
console.log(alphabet.includes("e")) // false
console.log([...alphabet].sort()) // ["a", "b", "c", "d"]
console.log([...alphabet].reverse()) // ["b", "d", "a", "c"]

var numbers = [1, 2, 3]
numbers.append(4)

var names = Array<String>()
names.append("Ali")
print(names[0]) // "Ali"

var grades = [Int]()
grades.append(73)

var alphabet: [String] = ["a", "b", "c", "d"]
print(alphabet.count) // 4
print(alphabet.remove(at: 2)) // "c"
alphabet.removeAll()

alphabet = ["c", "a", "d", "b"]
print(alphabet.contains("e")) // false
print(alphabet.sorted()) // ["a", "b", "c", "d"]
print(alphabet.reversed()) // ReversedCollection<Array<String>>(_base: ["c", "a", "d", "b"])

Dictionaries

const ali = {
  name: "Ali",
  surname: "Veli",
  age: "20",
}
console.log(ali.name) // "Ali"
console.log(ali.surname) // "Veli"
console.log(ali.age) // "20"

const olympics = new Map()
olympics.set(2012, "London")
olympics.set(2016, "Rio")
olympics.set(2016, "Rio de Janeiro")
olympics.set(2021, "Tokyo")
console.log(olympics.get(2012)) // "London"
console.log(olympics.size) // 3

let ali = [
  "name": "Ali",
  "surname": "Veli",
  "age": "20",
]
print(ali["name", default: "Unknown"]) // Optional("Ali")
print(ali["surname", default: "Unknown"]) // Optional("Veli")
print(ali["age", default: "Unknown"]) // Optional("20")

var olympics = [Int: String]()
olympics[2012] = "London"
olympics[2016] = "Rio"
olympics[2016] = "Rio de Janeiro"
olympics[2021] = "Tokyo"
print(olympics[2012, default: "World"]) // Optional("London")
print(olympics.count) // 3

Sets

const names = new Set(["Ali", "Veli", "Ahmet"])
console.log(names) // Set { "Ali", "Veli", "Ahmet" }

const cities = new Set()
cities.add("İstanbul")
cities.add("İstanbul")
console.log(cities.has("İstanbul")) // true
console.log(cities.size) // 1
cities.add("Ankara")
console.log(Array.from(cities).sort()) // ["Ankara", "İstanbul"]

let names = Set(["Ali", "Veli", "Ahmet"])
print(names) // ["Ali", "Veli", "Ahmet"]

var cities = Set<String>()
cities.insert("İstanbul")
cities.insert("İstanbul")
print(cities.contains("İstanbul")) // true
print(cities.count) // 1
cities.insert("Ankara")
print(cities.sorted()) // ["Ankara", "İstanbul"]

Enums

const Weekday = Object.freeze({
  monday: Symbol("monday"),
  tuesday: Symbol("tuesday"),
  wednesday: Symbol("wednesday"),
  thursday: Symbol("thursday"),
  friday: Symbol("friday"),
})

enum Weekday {
  case monday
  case tuesday
  case wednesday
  case thursday
  case friday
}
var day = Weekday.monday
day = Weekday.tuesday
day = .wednesday

enum Weekend {
  case saturday, sunday
}

Type Annonations

const name: string = "Ali"
const score: number = 0
const pi: number = 3.141
const isAdmin: boolean = true
const albums: string[] = ["Century Child", "Human. :II: Nature."]
const olympics: Map<number, string> = new Map([
  [2012, "London"],
  [2016, "Rio"],
  [2021, "Tokyo"],
])
const books: Set<string> = new Set(["The Name of the Wind", "The Wise Man's Fear"])

let name: String = "Ali"
let score: Double = 0
let pi: Double = 3.141
let isAdmin: Bool = true
let albums: [String] = ["Century Child", "Human. :II: Nature."]
let olympics: [Int: String] = [2012: "London", 2016: "Rio", 2021: "Tokyo"]
let books: Set<String> = Set(["The Name of the Wind", "The Wise Man's Fear"])

Conditions

`if`/`else`

const age = 18
const isAdmin = true
if (age >= 18 && isAdmin) {
  console.log("You're authenticated")
} else if (age < 18) {
  console.log("You're not an adult")
} else if (!isAdmin) {
  console.log("Contact with an admin")
} else {
  console.log("You're unauthenticated")
}

let age = 18
let isAdmin = true
if age >= 18 && isAdmin {
  print("You're authenticated")
} else if age < 18 {
  print("You're not an adult")
} else if !isAdmin {
  print("Contact with an admin")
} else {
  print("You're unauthenticated")
}

`switch`/`case`

const num = 2
switch (num) {
  case 1:
    console.log("one")
    break
  case 2:
    console.log("two") // "two"
  case 3:
    console.log("three") // "three"
  default:
    console.log("4,5,6,...") // "4,5,6,..."
}

let num = 2
switch num {
case 1:
  print("one")
case 2:
  print("two") // "two"
  fallthrough
case 3:
  print("three") // "three"
  fallthrough
default:
  print("4,5,6,...") // "4,5,6,..."
}

Ternary Conditional Operator: `?:`

const age = 18
const canVote = age >= 18 ? "Y" : "N"
console.log(canVote) // "Y"

let age = 18
let canVote = age >= 18 ? "Y" : "N"
print(canVote) // "Y"

Loops

`for` Loop

const alphabet = ["a", "b", "c"]
for (const char of alphabet) {
  console.log(char) // "a", "b", "c"
}

const range = (from, to, { inclusive = true } = {}) => 
  Array(to - from + Number(inclusive)).fill(null).map((_, i) => i + from)
// range(3, 5) = 3...5
for (const num of range(3, 5)) {
  if (num === 5) break
  if (num % 2 === 1) continue
  console.log(num) // 2, 4
}
// range(3, 5, { inclusive: false }) = 3..<5
for (const num of range(3, 5, { inclusive: false })) {
  console.log(num) // 3, 4
}

let alphabet = ["a", "b", "c"]
for char in alphabet {
  print(char) // "a", "b", "c"
}

for num in 1...10 {
  if num == 5 {
    break
  }
  if num % 2 == 1 {
    continue
  }
  print(num) // 2, 4
}
for num in 3..<5 {
  print(num) // 3, 4
}

`while` Loop

let num = 0
while (num !== 4) {
  num = Math.ceil(Math.random() * 10)
  console.log(num) // 1 to 10
}

var num = 0
while num != 4 {
  num = Int.random(in: 1...10)
  print(num) // 1 to 10
}

Functions

const isEven = ({ num }) => {
  const res = num % 2 === 0
  return res
}
console.log(isEven({ num: 3 })) // false

func isEven(num: Int) -> Bool {
  let res = num % 2 == 0
  return res
}
print(isEven(num: 3)) // false

Return Multiple Values

const getUserArray = () => ["Floor", "Jansen"]
const userArray = getUserArray()
console.log(`${userArray[0]} ${userArray[1]}`) // "Floor Jansen"

const getUserDict = () => ({ name: "Floor", surname: "Jansen" })
const userDict = getUserDict()
console.log(`${userDict.name} ${userDict.surname}`) // "Floor Jansen"

const getUserTuple = () => ["Floor", "Jansen"]
const userTuple = getUserTuple()
console.log(`${userArray[0]} ${userArray[1]}`) // "Floor Jansen"

const getUserNamedTuple = () => ({ name: "Floor", surname: "Jansen" })
const { name, surname } = getUserNamedTuple()
console.log(`${name} ${surname}`) // "Floor Jansen"

func getUserArray() -> [String] {
  ["Floor", "Jansen"]
}
let userArray = getUserArray()
print("\(userArray[0]) \(userArray[1])") // "Floor Jansen"

func getUserDict() -> [String: String] {
  ["name": "Floor", "surname": "Jansen"]
}
let userDict = getUserDict()
print("\(userDict["name", default: "Ali"]) \(userDict["surname", default: "Veli"])") // "Floor Jansen

func getUserTuple() -> (String, String) {
  ("Floor", "Jansen")
}
let userTuple = getUserTuple()
print("\(userTuple.0) \(userTuple.1)") // "Floor Jansen"

func getUserNamedTuple() -> (name: String, surname: String) {
  // ("Floor", "Jansen") // This is valid also
  (name: "Floor", surname: "Jansen")
}
let (name, _) = getUserNamedTuple()
let (_, surname) = getUserNamedTuple()
print("\(name) \(surname)") // "Floor Jansen"

Customize Parameter Labels

const isOdd = (num) => {
  return num % 2 === 1
}
console.log(isOdd(3)) // true

const printTimesTable = ({ for: num }) => {
  for (let i = 1; i <= 3; i++) {
    console.log(`${i} x ${num} = ${i * num}`)
  }
}
printTimesTable({ for: 5 }) // "1 x 5 = 5", "2 x 5 = 10", "3 x 5 = 15"

func isOdd(_ num: Int) -> Bool {
  num % 2 == 1
}
print(isOdd(3)) // true

func printTimesTable(for num: Int) {
  for i in 1...3 {
    print("\(i) x \(num) = \(i * num)")
  }
}
printTimesTable(for: 5) // "1 x 5 = 5", "2 x 5 = 10", "3 x 5 = 15"

Default Values for Parameters

const printNumbers = ({ from, to = 10 }) => {
  for (let i = from; i <= to; i++) console.log(i)
}
printNumbers({ from: 8 }) // 8, 9, 10

func printNumbers(from: Int, to: Int = 10) {
  for i in from...to {
    print(i)
  }
}
printNumbers(from: 8) // 8, 9, 10

Handle Errors in Functions

const PasswordError = Object.freeze({
  short: Symbol("short"),
  obvious: Symbol("obvious"),
})

const checkPassword = (password) => {
  const length = password.length
  if (length < 5) throw PasswordError.short
  if (password === "12345") throw PasswordError.obvious

  if (length < 8) return "Ok"
  if (length < 10) return "Good"
  return "Excellent"
}

try {
  const res = checkPassword("12345")
  console.log(res)
} catch (err) {
  if (err === PasswordError.short) {
    console.log("Short password")
  } else if (err === PasswordError.obvious) {
    console.log("Try a stronger password.") // "Try a stronger password."
  } else {
    console.log("An error occured.")
  }
}

enum PasswordError: Error {
  case short, obvious
}

func checkPassword(_ password: String) throws -> String {
  let count = password.count
  if count < 5 {
    throw PasswordError.short
  }

  if password == "12345" {
    throw PasswordError.obvious
  }

  if count < 8 {
    return "Ok"
  } 
  if count < 10 {
    return "Good"
  }
  return "Excellent"
}

do {
  let res = try checkPassword("12345")
  print(res)
} catch PasswordError.short {
  print("Short password")
} catch PasswordError.obvious {
  print("Try a stronger password.") // "Try a stronger password."
} catch {
  print("An error occured")
}

Closures

const sayHi = () => console.log("Hi!")
sayHi() // "Hi"

const greet = (name) => `Hi, ${name}!`
console.log(greet("Ali")) // "Hi, Ali!"

const sorted = [3, 1, 2].sort((a, b) => a - b)
console.log(sorted) // [1, 2, 3]

let sayHi = {
  print("Hi!")
}
sayHi() // "Hi!"

let greet = { (name: String) -> String in
  "Hi, \(name)"
}
print(greet("Ali")) // "Hi, Ali!"

let sorted = [3, 1, 2].sorted(by: { (a: Int, b: Int) -> Bool in
  a < b
})
print(sorted) // [1, 2, 3]

Trailing Closure

const sorted = [3, 1, 2].sort((a, b) => a - b)
console.log(sorted) // [1, 2, 3]

const reversed = [3, 1, 2].sort((a, b) => b - a)
console.log(reversed) // [3, 2, 1]

let sorted = [3, 1, 2].sorted { a, b in 
  a < b
}
print(sorted) // [1, 2, 3]

let reversed = [3, 1, 2].sorted { $0 > $1 }
print(reversed) // [3, 2, 1]

Functions as Parameters

const makeArray = ({ size, using: generator }) => {
  const numbers = []
  for (let i = 0; i < size; i++) {
    numbers.push(generator())
  }
  return numbers;
}

func makeArray(size: Int, using generator: () -> Int) -> [Int] {
  var numbers = [Int]()
  for _ in 0..<size {
    numbers.append(generator())
  }
  return numbers
}

Example 1

const arr = makeArray({ size: 3, using: () => Math.floor(Math.random() * 10) })
console.log(arr) // [4, 2, 8]

let arr = makeArray(size: 3) { Int.random(in: 1..<10) }
print(arr) // [8, 6, 2]

Example 2

const generateNumber = () => Math.floor(Math.random() * 10)
const arr = makeArray({ size: 3, using: generateNumber })
console.log(arr) // [5, 0, 4]

func generateNumber() -> Int { Int.random(in: 0..<10 )}
let arr = makeArray(size: 3, using: generateNumber)
print(arr) // [7, 9, 3]

Example 3

const printThreeSteps = ({ first, second, third }) => {
  console.log("1st:")
  first()
  console.log("2nd:")
  second()
  console.log("3rd:")
  third()
  console.log("Completed")
}
printThreeSteps({
  first: () => console.log("a"),
  second: () => console.log("b"),
  third: () => console.log("c"),
}) // "1st:", "a", "2nd:", "b", "3rd:", "c", "Completed"

func printThreeSteps(first: () -> Void, second: () -> Void, third: () -> Void) {
  print("1st:")
  first()
  print("2nd:")
  second()
  print("3rd:")
  third()
  print("Completed")
}
printThreeSteps {
  print("a")
} second: {
  print("b")
} third: {
  print("c")
} // "1st:", "a", "2nd:", "b", "3rd:", "c", "Completed"

How to Chain Functions

const arr = [4, 3, 2, 5, 1]
  .filter(x => x % 2 === 0)
  .map(x => x * x)
  .sort((x, y) => x - y)
console.log(arr) // [4, 16]

let arr = [4, 3, 2, 5, 1].filter { 
  $0 % 2 == 0
}.map {
  $0 * $0
}.sorted {
  $0 < $1
}
print(arr) // [4, 16]

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README.md

README.md

Swift for JavaScript Developers

Variables

Constants

Strings

Numbers

Decimal Numbers

Booleans

Arrays

Dictionaries

Sets

Enums

Type Annonations

Conditions

`if`/`else`

`switch`/`case`

Ternary Conditional Operator: `?:`

Loops

`for` Loop

`while` Loop

Functions

Return Multiple Values

Customize Parameter Labels

Default Values for Parameters

Handle Errors in Functions

Closures

Trailing Closure

Functions as Parameters

Example 1

Example 2

Example 3

How to Chain Functions

Files

README.md

Latest commit

History

README.md

File metadata and controls

Swift for JavaScript Developers

Variables

Constants

Strings

Numbers

Decimal Numbers

Booleans

Arrays

Dictionaries

Sets

Enums

Type Annonations

Conditions

if/else

switch/case

Ternary Conditional Operator: ?:

Loops

for Loop

while Loop

Functions

Return Multiple Values

Customize Parameter Labels

Default Values for Parameters

Handle Errors in Functions

Closures

Trailing Closure

Functions as Parameters

Example 1

Example 2

Example 3

How to Chain Functions

`if`/`else`

`switch`/`case`

Ternary Conditional Operator: `?:`

`for` Loop

`while` Loop