JavaScript Maps
JavaScript Maps
In JavaScript Maps 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:
