Why do we need Map when we already have Object in JavaScript?

const dictionary = {
    'ja': {
        'Ninjas for hire': 'Ninjas for hire',
    },
    'zh': {
        'Ninjas for hire': 'Ninjas for hire',
    },
    'ko': {
        'Ninjas for hire': '고용닌자',
    }
}

console.log(dictionary.ja['Ninjas for hire']) // ninjas for hireconsole.log(dictionary.zh['Ninjas for hire']) // ninjas for hireconsole.log(dictionary.ko['Ninjas for hire']) // ninjas for hireconsole.log(dictionary.ko['Ninjas for hire']) // ninjas for hire

console.log(dictionary.ko['constructor']) // ƒ Object() { [native code] }

Object.setPrototypeOf(dictionary.ko, null)
console.log(dictionary.ko['constructor']) // undefined

/* HTML part <div id="firstElement"></div>
<div id="secondElement"></div>
*/

const firstElement = document.getElementById('firstElement')
const secondElement = document.getElementById('secondElement')

const map = {}

map[firstElement] = {
    data: 'firstElement'
}
map[secondElement] = {
    data: 'secondElement'
}

console.log(map[firstElement].data) // secondElement
console.log(map[secondElement].data) // secondElement

function People(name) {
    this.name = name
}
const zhangsan = new People('zhangsan')
const xiaoming = new People('xiaoming')
const lihua = new People('lihua')
// Create a Map
const map = new Map()
// Create a Map and initialize it to convert the two-dimensional key-value array into a Map object const map1 = new Map([
    ['key1', 'val1'],
    ['key2', 'val2'],
])
// Convert Map to a two-dimensional array console.log(Array.from(map1)) // [ [ 'key1', 'val1' ], [ 'key2', 'val2' ] ]
// Set the key-value mapping relationship map.set(zhangsan, { region: 'HB' })
map.set(xiaoming, { region: 'HN' })
// Get the corresponding value according to the key console.log(map.get(zhangsan)) // { region: 'HB' }
console.log(map.get(xiaoming)) // { region: 'HN' }
// Get the non-existent key and get undefined
console.log(map.get(lihua)) // undefined
// Use the has function to determine whether the specified key exists console.log(map.has(lihua)) // false
console.log(map.has(xiaoming)) // true
//map stores the number of mappingsconsole.log(map.size) // 2
// delete delete key
map.delete(xiaoming)
console.log(map.has(xiaoming)) // false
console.log(map.size) // 1
// clear clears the map
map.clear()
console.log(map.size) // 0

const zhangsan = { name: 'zhangsan' }
const xiaoming = { name: 'xiaoming' }
const map = new Map()
map.set(zhangsan, { region: 'HB' })
map.set(xiaoming, { region: 'HN' })
// Each key-value pair returns an array of [key, value] for (let item of map) { // = for (let item of map.entries()) {
    console.log(item)
    // [ { name: 'zhangsan' }, { region: 'HB' } ]
    // [ { name: 'xiaoming' }, { region: 'HN' } ]
}
// Traverse the key
for (let key of map.keys()) {
    console.log(key)
    // { name: 'zhangsan' }
    // { name: 'xiaoming' }
}
// Traverse value
for (let key of map.values()) {
    console.log(key)
    // { region: 'HB' }
    // { region: 'HN' }
}
// Iterate over the Map using the forEach() method
map.forEach(function(value, key) {
    console.log(key, value)
    // { name: 'zhangsan' } { region: 'HB' }
    // { name: 'xiaoming' } { region: 'HN' }
})

Object.is(NaN, NaN) // true
Object.is(0, -0) // false

map.set(NaN, 0)
map.set(0, 0)
console.log(map.has(NaN)) // true
console.log(map.has(-0)) // true

let original = new Map([
    [1, {}]
])
let clone = new Map(original) // Clone Map

console.log(clone.get(1)); // {}
console.log(original === clone) // false
console.log(original.get(1) === clone.get(1)) // true

let first = new Map([
    [1, 'one'],
    [2, 'two'],
    [3, 'three'],
]);
let second = new Map([
    [1, 'uno'],
    [2, 'dos']
]);
// When merging two Map objects, if there are duplicate key values, the latter will overwrite the former.
// The spread operator essentially converts a Map object into an array.
let merged = new Map([...first, ...second]);

console.log(merged.get(1)); // uno
console.log(merged.get(2)); // dos
console.log(merged.get(3)); // three

// Initialize Map(1) {"key1" => "val1"}
const originMap = new Map([['key1', 'val1']])
//Serialize "[[\"key1\",\"val1\"]]"
const mapStr = JSON.stringify(Array.from(originMap.entries())) 
// Deserialize Map(1) {"key1" => "val1"}
const cloneMap = new Map(JSON.parse(mapStr))