Map in Node.js

Complete guide to JavaScript Map: creation, CRUD operations, key existence checks, size, keys & values retrieval, traversal, merging maps and objects, and comparison with plain objects.

Map Basics

Map is a built-in JavaScript data structure for storing key-value pairs. It preserves insertion order and allows keys of any data type.

1. Creating an Empty Map

Use the Map constructor.

2. Setting a Key-Value Pair

Use set(key, value).

3. Checking if a Key Exists

Use has(key).

4. Accessing Value on a Specific Key

Use get(key).

5. Updating Value on a Specific Key

Call set() on an existing key.

6. Deleting a Key-Value Pair

Use delete(key).

7. Clearing the Map

Use clear().

8. Getting Map Size

Use the size property.

Map Keys & Values

Map provides iterators to access keys and values separately.

1. Getting Keys List of a Map

Use map.keys().

2. Getting Values List of a Map

Use map.values().

Traversing a Map

Maps and objects both support traversal, but through different APIs.

1. Traversing a Map using for...of

Iterate over [key, value] pairs.

2. Traversing a Map using forEach

Callback-based traversal.

3. Traversing an Object using Object.entries

Use for...of with Object.entries.

Merging Maps and Objects

Maps and objects can be merged using spread syntax.

1. Merging Two Maps

Use spread operator.

2. Merging Two Objects

Use object spread.