JavaScript Map Reference Manual

Map is a data structure that stores key-value pairs, where the key can be any data type.

Map will remember the original insertion order of keys.

Map Methods and Properties

Method/Property Description
new Map() Create a new Map object.
clear() Removes all elements from the Map.
delete() Removes elements from the Map by key.
entries() Returns an iterator object containing [key, value] pairs in the Map.
forEach() Calls a callback function for each key/value pair in the Map.
get() Gets the value of a specific key in the Map.
groupBy() Groups object elements based on the value returned by the callback function.
has() Returns true if a key exists in the Map.
keys() Returns an iterator object containing the keys in the Map.
set() Sets a value for a specific key in the Map.
size Returns the number of elements in the Map.
values() Returns an iterator object containing the values in the Map.

Instance

// Create Map

  
  
  
]

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Example 2

You can use set() Methods to add elements to Map:

// Create Map
const fruits = new Map();
// Set the value of Map
fruits.set("apples", 500);
fruits.set("bananas", 300);
fruits.set("oranges", 200);

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Example 3

You can use get() Methods to get elements from Map:

// Get the value of "apples"
let value = fruits.get("apples");
JavaScript Objects vs Maps

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The difference between JavaScript objects and Map

The difference between JavaScript objects and Map:

Object Map
Cannot be iterated directly Can be iterated directly
Size attribute does not exist Size attribute exists
Keys must be strings (or symbols) Keys can be of any data type
The order of keys is not clear Keys are sorted in the order of insertion
Default key exists No default key