map.md

chapter	25
pageNumber	247
description	Certainly! Let's discuss the `let` and `const` declarations in the context of ES6 (ECMAScript 2015) and compare them to their ES5 counterparts.

Map

Map is a collection of keyed data items, just like an Object. But the main difference is that Map allows keys of any type.

Method/Property	Description
new Map()	Creates a new Map object.
map.set(key, value)	Stores the value in the map object under the key.
map.get(key)	Returns the value associated with the key, or undefined if the key doesn't exist.
map.has(key)	Returns true if the map contains the key, otherwise returns false.
map.delete(key)	Removes the element (key/value pair) from the map specified by the key.
map.clear()	Removes all elements from the map.
map.size	Returns the number of elements (key/value pairs) in the map.

An example of Map() with its various methods and properties is shown below.

let map = new Map();

map.set('1', 'str1');   // a string key
map.set(1, 'num1');     // a numeric key
map.set(true, 'bool1'); // a boolean key

// remember the regular Object? it would convert keys to string
// Map keeps the type, so these two are different:
alert( map.get(1)   ); // 'num1'
alert( map.get('1') ); // 'str1'

alert( map.size ); // 3

The differences from a regular Object:

• Any keys, objects can be keys.

• Additional convenient methods, the size property.

Maps are a versatile and powerful data structure that provides key-value pairs for efficient data management. Maps are often a preferred choice over plain objects for tasks involving key-value associations, as they provide better control and performance.