Source: Set in JavaScript
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Set objects are collections of values. You can iterate through the elements of a set in insertion order. A value in the Set may only occur once; it is unique in the Set’s collection.
Code e.g
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
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)