JavaScript Map

Key-Value Pairs:

• Maps store collections of key-value pairs where each key is unique.
• Keys can be of any data type, including objects and primitive values.

Iterability:

• Maps maintain the order of insertion of key-value pairs, making them iterable in the order of insertion.

Example: Creating a Map

const myMap = new Map();
myMap.set('name', 'John');
myMap.set('age', 30);

Accessing Values:

• Use the get() method to retrieve the value associated with a specific key.
• Use the has() method to check if a key exists in the map.

Example: Accessing Values

console.log(myMap.get('name')); // Output: John
console.log(myMap.has('age')); // Output: true

Size:

• The size property returns the number of key-value pairs in the map.

Example: Size

console.log(myMap.size); // Output: 2

Iterating over a Map:

• Use methods like forEach(), for...of loop, or the entries(), keys(), and values() iterators to iterate over a map.

Example: Iterating over a Map

myMap.forEach((value, key) => {
  console.log(`${key}: ${value}`);
});

 

Key Points

• JavaScript Map is a collection of key-value pairs with unique keys.
• Maps are iterable and maintain the order of insertion.
• They provide efficient methods for adding, retrieving, and iterating over key-value pairs.
• Maps are commonly used for storing data where the relationship between keys and values is important.