JavaScript Maps
JavaScript Maps are data structures that store key-value pairs, where each key is unique and maps to a corresponding value.
Maps in JavaScript were introduced in ECMAScript 6, and they provide a more flexible alternative to objects for mapping keys to values.
Essential Map Methods
| Method | Description |
|---|---|
| new Map() | Creates a new Map |
| set() | Sets the value for a key in a Map |
| get() | Gets the value for a key in a Map |
| delete() | Removes a Map element specified by the key |
| has() | Returns true if a key exists in a Map |
| forEach() | Calls a function for each key/value pair in a Map |
| entries() | Returns an iterator with the [key, value] pairs in a Map |
| Property | Description |
| size | Returns the number of elements in a Map |
How to Create a Map
For create a new Map, you can use the new keyword and the Map() constructor:
let myMap = new Map();
- You can add key-value pairs to the map using the
set()method:
myMap.set("key1", "value1");
myMap.set("key2", "value2");
- You can also chain the
set()method to add multiple key-value pairs in a single line of code:
myMap.set("key1", "value1").set("key2", "value2");
- To retrieve a value from the map, you can use the
get()method and pass in the key:
console.log(myMap.get("key1")); // Output: "value1"
- You can also check if a key exists in the map using the
has()method:
console.log(myMap.has("key1")); // Output: true
- To remove a key-value pair from the map, you can use the
delete()method and pass in the key:
myMap.delete("key1");
console.log(myMap.has("key1")); // Output: false
- You can also clear all key-value pairs from the map using the
clear()method:
myMap.clear();
console.log(myMap.size); // Output: 0
- Maps also have a
sizeproperty that returns the number of key-value pairs in the map:
console.log(myMap.size); // Output: 1
Overall, Maps in JavaScript are a powerful tool for working with key-value data and provide a more flexible alternative to objects.