Introduction to JavaScript Maps

JavaScript Maps are a built-in object type that allows you to store key-value pairs. Unlike arrays, which use numeric indices, maps can use any value as a key, making them more versatile for data storage and retrieval. In this article, we will introduce Maps in JavaScript and provide examples to illustrate their usage.

Creating a Map

You can create a Map in JavaScript by using the Map() constructor. For example:

    
      var map = new Map();
    
  

Adding and Retrieving Values

To add a key-value pair to a Map, you can use the set() method. To retrieve a value based on a key, you can use the get() method. For example:

    
      var map = new Map();

      map.set("name", "John");
      map.set("age", 30);

      console.log(map.get("name")); // "John"
    
  

Working with JavaScript Maps

JavaScript Maps provide various methods for working with key-value pairs. These methods allow you to add, retrieve, delete, and iterate over the entries in a Map. In this article, we will explore the commonly used methods and operations available with JavaScript Maps, along with examples.

Adding and Retrieving Values

You can add key-value pairs to a Map using the set() method. To retrieve a value based on a key, you can use the get() method. For example:

    
      var map = new Map();

      map.set("name", "John");
      map.set("age", 30);

      console.log(map.get("name")); // "John"
    
  

Deleting Values

To delete a key-value pair from a Map, you can use the delete() method. For example:

    
      var map = new Map();

      map.set("name", "John");
      map.set("age", 30);

      map.delete("age");
    
  

Iterating over a Map

Maps can be iterated using various iteration methods, such as forEach() and for-of loop. These methods allow you to perform operations on each entry of the Map. For example:

    
      var map = new Map();

      map.set("name", "John");
      map.set("age", 30);

      map.forEach(function(value, key) {
        console.log(key + ": " + value);
      });

      for (var entry of map) {
        console.log(entry[0] + ": " + entry[1]);
      }
    
  

JavaScript Map Operations

JavaScript Maps provide several operations and methods to manipulate, combine, and compare maps. These operations include merging maps, checking map size, and checking key existence. In this article, we will explore the different map operations available in JavaScript Maps, along with examples.

Merging Maps

You can merge two maps into a single map using the set() method in a loop. For example:

    
      var map1 = new Map();
      var map2 = new Map();

      map1.set("name", "John");
      map1.set("age", 30);

      map2.set("city", "New York");
      map2.set("country", "USA");

      var mergedMap = new Map();

      map1.forEach(function(value, key) {
        mergedMap.set(key, value);
      });

      map2.forEach(function(value, key) {
        mergedMap.set(key, value);
      });
    
  

Checking Map Size

To get the size (number of entries) of a map, you can use the size property. For example:

    
      var map = new Map();

      map.set("name", "John");
      map.set("age", 30);

      console.log(map.size); // 2
    
  

JavaScript Map Iteration Methods

JavaScript Maps provide several iteration methods that allow you to iterate over the entries, keys, and values of a Map. These methods include forEach(), keys(), values(), and entries(). In this article, we will explore the different iteration methods available in JavaScript Maps, along with examples.

Iterating over Map Entries

To iterate over the entries of a Map, you can use the forEach() method or the entries() method. For example:

    
      var map = new Map();

      map.set("name", "John");
      map.set("age", 30);

      map.forEach(function(value, key) {
        console.log(key + ": " + value);
      });

      for (var entry of map.entries()) {
        console.log(entry[0] + ": " + entry[1]);
      }
    
  

Iterating over Map Keys

To iterate over the keys of a Map, you can use the keys() method. For example:

    
      var map = new Map();

      map.set("name", "John");
      map.set("age", 30);

      for (var key of map.keys()) {
        console.log(key);
      }