EcmaScript | ES6 map.js

// Map - data structure with key-value pairs, where keys can be any type
const map = new Map()

map.set('1', 'string')
   .set(1, 'number')
   .set(true, 'boolean')

const obj = { name: 'John' }
map.set(obj, 'John')

const symbol1 = Symbol()
const symbol2 = Symbol()
map.set(symbol1, 'Symbol 1')
   .set(symbol2, 'Symbol 2')

console.log(map.get('1')) // Expected output: string
console.log(map.get(1)) // Expected output: number
console.log(map.get(true)) // Expected output: boolean
console.log(map.get(obj)) // Expected output: John
console.log(map.get(symbol1)) // Expected output: Symbol 1
console.log(map.get(symbol2)) // Expected output: Symbol 2

console.log(map.size) // Expected output: 6

console.log(map.has(1)) // Expected output: true
console.log(map.has(3)) // Expected output: false

map.delete(1)
console.log(map.size) // Expected output: 5
console.log(map.has(1)) // Expected output: false

// It's possible to iterate map with for/of loop
for (const [key, value] of map) {
    console.log(key)
    console.log(value)
}