JavaScript Maps
JavaScript Maps
A Map is a collection of key-value pairs in JavaScript. Unlike objects, Maps allow:
✔ Any type of key (objects, functions, numbers, strings)
✔ Values to be stored in insertion order
✔ Easy size checking
🧩 Creating a Map
➕ Adding Key-Value Pairs
Use the .set() method:
🔍 Getting Values
❓ Checking Keys
🗑 Removing Items
🧹 Clear All Items
📏 Size of a Map
🔁 Iterating Through a Map
Loop through keys and values:
Using forEach():
📌 Useful Methods Summary
| Method | Description |
|---|---|
set(key, value) |
Adds or updates entry |
get(key) |
Returns value for the key |
has(key) |
Checks if key exists |
delete(key) |
Removes key/value |
clear() |
Removes all entries |
size |
Number of items |
🆚 Map vs Object
| Feature | Map | Object |
|---|---|---|
| Key type | Any type | String/symbol only |
| Ordered | Yes | No guarantee |
| Iterable | Yes | No (needs conversion) |
| Size tracking | size property |
Must count manually |
⭐ Practical Example: Counting Occurrences
Output:
