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let mySet = new Set()
mySet.add(1) // Set [ 1 ]
mySet.add(5) // Set [ 1, 5 ]
mySet.add(5) // Set [ 1, 5 ]
mySet.add('some text') // Set [ 1, 5, 'some text' ]
let o = {a: 1, b: 2}
mySet.add(o)
mySet.add({a: 1, b: 2}) // o is referencing a different object, so this is okay
mySet.has(1) // true
mySet.has(3) // false, since 3 has not been added to the set
mySet.has(5) // true
mySet.has(Math.sqrt(25)) // true
mySet.has('Some Text'.toLowerCase()) // true
mySet.has(o) // true
mySet.size // 5
mySet.delete(5) // removes 5 from the set
mySet.has(5) // false, 5 has been removed
mySet.size // 4, since we just removed one value
console.log(mySet)
// logs Set(4) [ 1, "some text", {…}, {…} ] in Firefox
// logs Set(4) { 1, "some text", {…}, {…} } in Chrome
Iterating Sets
// iterate over items in set
// logs the items in the order: 1, "some text", {"a": 1, "b": 2}, {"a": 1, "b": 2}
for (let item of mySet) console.log(item)
// logs the items in the order: 1, "some text", {"a": 1, "b": 2}, {"a": 1, "b": 2}
for (let item of mySet.keys()) console.log(item)
// logs the items in the order: 1, "some text", {"a": 1, "b": 2}, {"a": 1, "b": 2}
for (let item of mySet.values()) console.log(item)
// logs the items in the order: 1, "some text", {"a": 1, "b": 2}, {"a": 1, "b": 2}
// (key and value are the same here)
for (let [key, value] of mySet.entries()) console.log(key)
// convert Set object to an Array object, with Array.from
let myArr = Array.from(mySet) // [1, "some text", {"a": 1, "b": 2}, {"a": 1, "b": 2}]
// the following will also work if run in an HTML document
mySet.add(document.body)
mySet.has(document.querySelector('body')) // true
// converting between Set and Array
mySet2 = new Set([1, 2, 3, 4])
mySet2.size // 4
[...mySet2] // [1, 2, 3, 4]
// intersect can be simulated via
let intersection = new Set([...set1].filter(x => set2.has(x)))
// difference can be simulated via
let difference = new Set([...set1].filter(x => !set2.has(x)))
// Iterate set entries with forEach()
mySet.forEach(function(value) {
console.log(value)
})
// 1
// 2
// 3
// 4
Implementing basic set operations
function isSuperset(set, subset) {
for (let elem of subset) {
if (!set.has(elem)) {
return false
}
}
return true
}
function union(setA, setB) {
let _union = new Set(setA)
for (let elem of setB) {
_union.add(elem)
}
return _union
}
function intersection(setA, setB) {
let _intersection = new Set()
for (let elem of setB) {
if (setA.has(elem)) {
_intersection.add(elem)
}
}
return _intersection
}
function symmetricDifference(setA, setB) {
let _difference = new Set(setA)
for (let elem of setB) {
if (_difference.has(elem)) {
_difference.delete(elem)
} else {
_difference.add(elem)
}
}
return _difference
}
function difference(setA, setB) {
let _difference = new Set(setA)
for (let elem of setB) {
_difference.delete(elem)
}
return _difference
}
// Examples
let setA = new Set([1, 2, 3, 4])
let setB = new Set([2, 3])
let setC = new Set([3, 4, 5, 6])
isSuperset(setA, setB) // => true
union(setA, setC) // => Set [1, 2, 3, 4, 5, 6]
intersection(setA, setC) // => Set [3, 4]
symmetricDifference(setA, setC) // => Set [1, 2, 5, 6]
difference(setA, setC)
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