DoctorDerek

// Set up a number array with duplicate values
const myNumberArray = [37, 37, 370, 3700, 3700, 37]

// Using Set with different approaches
// 1) Set using for...of loop
const myNumberSetForOf = new Set()
for (const myNumber of myNumberArray) {
  myNumberSetForOf.add(myNumber)
}
// 2) Set using .forEach()

DoctorDerek

Array.from(new Set([37, 37, 3700, 3700])) // [37,3700]

DoctorDerek

// Different JavaScript objects have different
// object references, even with the same values:
const someArray = [1]
const otherArray = [1]

// Different references even though both are [1]
console.log(`Does someArray === someArray?`)
console.log(`${someArray === someArray}`)
// Output: true because of same object reference
console.log(`Does someArray === otherArray?`)

DoctorDerek

[...new Set([3, 4, 5, 5])] // [3,4,5]

DoctorDerek

const emojiSet = new Set(["🙋🏼", "🦾", "🦿", "🙋🏼"])

//  Use Set.prototype.keys() or Set.prototype.values()
const emojiIterator = emojiSet.values()
// You can use a for...of loop with an Iterator object
for (const emoji of emojiIterator) {
  console.log(emoji)
}
// emojiSet.keys() is equivalent to: emojiSet.values()
for (const emoji of emojiSet.keys()) {

DoctorDerek

// You can use Object.values() with Set to find unique
// values in an object, but keys are always unique.
const myObject = { hello: "🌏", hi: "🌏", howdy: "🚯" }

console.log(new Set(Object.keys(myObject)))
// Output: Set(3) [ "hello", "hi", "howdy" ]
console.log(new Set(Object.values(myObject)))
// Output: Set(2) [ "🌏", "🚯" ]
console.log(new Set(Object.entries(myObject)))
// Output: Set(3) [[ "hello", "🌏" ], ...]

DoctorDerek

const yearsArray = [{ year: 1999 }, { year: 2000 }, { year: 1999 }]
const arrayOfOnlyYears = yearsArray.map((object) => object.year)
const uniqueYears = [...new Set(arrayOfOnlyYears)]
console.log(uniqueYears) // [1999,2000]

DoctorDerek

// This array contains 2 objects repeated twice each.
const objectsArray = [
  { id: 1, emoji: "🎸" },
  { id: 2, emoji: "🎷" },
  { id: 1, emoji: "🎸" },
  { id: 2, emoji: "🎷" },
]
// Each of these objects has a different object reference.
// That means each object is unique according to Set:
console.log(`${objectsArray.length} objects`)

DoctorDerek

const uniqueObjectsOneLiner = [
  ...new Set(objectsArray.map((o) => JSON.stringify(o))),
].map((string) => JSON.parse(string))
console.log(`${uniqueObjectsOneLiner.length} objects`)
// Output: 2 objects
console.log(...uniqueObjectsOneLiner)
// [ { id: 1, emoji: "🎸" }, { id: 2, emoji: "🎷" } ]

DoctorDerek

// Create an array with three Date objects:
const datesArray = [
  new Date(3005, 00, 01),
  new Date(3001, 00, 01),
  new Date(3001, 00, 01),
]
// Note that the second parameter to the Date()
// constructor is a monthIndex, so 0 is January.

// Output the dates by using .map() and .toDateString():