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Map in Javascript

Map in Javascript

08 Aug 2024
Beginner
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8 min read
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JavaScript Map

The Map object is a strong and adaptable collection type that lets you store key-value pairs in JavaScript. In contrast to conventional objects, maps preserve the order in which their elements are inserted and can use any kind of data as a key. Because of this, Map is an adaptable tool for a wide range of programming situations where unique keys and ordered data storage are crucial.

In this JavaScript tutorial, We are going to explore more about the map in JavaScript including understanding JavaScript Map, examples of JavaScript map, and methods of JavaScript Map.

What is a JavaScript Map?

  • In JavaScript, a Map is an integrated object that stores key-value pairs.
  • The map is more flexible than objects since keys can be of any kind, unlike objects and functions, which can only have strings and symbols. Y
  • You may also simply iterate over the elements in the order they were added because Map objects are iterable.

Diagram of JavaScript Map

Examples of JavaScript Map

Here are a few examples to illustrate how Map works:

Example

// Creating a new Map
let map = new Map();

// Adding key-value pairs
map.set('name', 'Alice');
map.set('age', 25);
map.set(1, 'one');

// Accessing values
console.log(map.get('name')); // Alice
console.log(map.get(1)); // one

// Iterating over the map
for (let [key, value] of map) {
    console.log(`${key} => ${value}`);
}
    

Output

Alice
one
name => Alice
age => 25
1 => one

JavaScript Map Methods

Map offers several ways for users to engage with its data:
  • set(key, value): Inserts a new element using the given value and key.
  • get(key): Gives back the value connected to the given key.
  • has(key): Determines if the map contains a key.
  • delete(key): Eliminates the element linked to the given key.
  • clear(): Clears the map of all elements. size: Gives the total number of items of the map.

Example of the map with the implementation of map methods

Here, we have written a program which includes set(),delete(),clear() methods

Example

map.set('city', 'New York');
console.log(map.has('city')); // true
map.delete('age');
console.log(map.size); // 3
map.clear();
console.log(map.size); // 0

Creating and Initializing a Map

Creating and initializing a Map is straightforward, Either use an array of arrays to initialize the map, or instantiate it and add key-value pairs directly.

Example


// Using the Map constructor
let map = new Map([
    ['name', 'Alice'],
    ['age', 25]
]);
// Adding elements
map.set('location', 'New York');

Advanced Operations with JavaScript Map

1. Cloning and Merging Maps

The spread operator and the new Map constructor can be used to duplicate a map. The set method can be used to merge maps.

Example


let map1 = new Map([
    ['a', 1],
    ['b', 2]
]);
// Cloning map
let map2 = new Map(map1);

// Merging maps
let map3 = new Map([...map1, ...map2]);

2. Using Nested Maps

Map objects have the ability to hold additional maps, enabling intricate layered systems.

Example


let nestedMap = new Map();
nestedMap.set('user', new Map([
    ['name', 'Alice'],
    ['age', 25]
]));

console.log(nestedMap.get('user').get('name')); // Alice

Performance-Related Issues 

Take into account a map's performance attributes before using it: 

  •  In general, insertion and lookup in a map operate more quickly than in an object. 
  • Maps are perfect for ordered data since they preserve insertion order. 

Why and How to Use Maps in JavaScript? 

  • When you need keys of any kind, use Map instead of Unique Keys. 
  • When the sequence of the items is crucial, use the map. 
  • Iterability: To make iterating over key-value pairs simple, use maps.
  •  JavaScript Maps are an excellent tool for storing configuration parameters in cases when the keys are not strings. 
  • Caching Data: To store data for easy access, use a map.
  •  Graph Representation: Use maps to represent graphs with key-value pairs for nodes and edges.

Common Use Cases of JavaScript Map

1. Storing configuration setting

 JavaScript Maps are an excellent tool for storing configuration parameters in cases when the keys are not strings.

2. Caching Data

To store data for easy access, use a map.

3. Graph Representation

Use maps to represent graphs with key-value pairs for nodes and edges.
Conclusion
JavaScript Map is an adaptable and strong structure that prioritizes order, flexibility, and performance when managing key-value pairs. With Map, you can efficiently manage your data regardless of the complexity of your data structures or collections. If you want to become a frontend developer don't forget to consider our Frontend Foundation Training Course.

FAQs

If you want the benefits of the return value or somehow you don't want to change the original array then proceed with the map() otherwise if you are just interested to iterate or perform the non-transformation process on the array, forEach() could be the better choice.

Map is generally faster than Object for operations that involve frequent additions and removals of key-value pairs.

Because the map() method provides a more concise and functional way to transform elements of an array into a new array.

If you need to store key-value pairs(hash or dictionary) use Map. If you're only using string-based keys and need maximum read performance, then objects might be a better choice.

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About Author
Shailendra Chauhan (Microsoft MVP, Founder & CEO at Scholarhat by DotNetTricks)

Shailendra Chauhan, Founder and CEO of ScholarHat by DotNetTricks, is a renowned expert in System Design, Software Architecture, Azure Cloud, .NET, Angular, React, Node.js, Microservices, DevOps, and Cross-Platform Mobile App Development. His skill set extends into emerging fields like Data Science, Python, Azure AI/ML, and Generative AI, making him a well-rounded expert who bridges traditional development frameworks with cutting-edge advancements. Recognized as a Microsoft Most Valuable Professional (MVP) for an impressive 9 consecutive years (2016–2024), he has consistently demonstrated excellence in delivering impactful solutions and inspiring learners.

Shailendra’s unique, hands-on training programs and bestselling books have empowered thousands of professionals to excel in their careers and crack tough interviews. A visionary leader, he continues to revolutionize technology education with his innovative approach.
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