The JavaScript Map object is used to map keys to values. It stores each element as key-value pair. It operates the elements such as search, update and delete on the basis of specified key.
iterable - It represents an array and other iterable object whose elements are in the form of key-value pair.
Map is a collection of keyed data items, just like an Object
. But the main difference is that Map
allows keys of any type.
Methods and properties are:
new Map()
– creates the map.map.set(key, value)
– stores the value by the key.map.get(key)
– returns the value by the key, undefined
if key
doesn’t exist in map.map.has(key)
– returns true
if the key
exists, false
otherwise.map.delete(key)
– removes the value by the key.map.clear()
– removes everything from the map.map.size
– returns the current element count.For instance:
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