Map

Map is an object in JavaScript that stores key-value pairs in their original insertion order.

A new map can be defined as follows. This map will store the number of fruits a store has.

const fruits = new Map();

Storing Data in Map

Key-value pairs are stored in Map using the .set() method.

fruits.set('Apples', 5);
fruits.set('Oranges', 8);

This stores in fruits, 5 apples and 8 oranges.

Retrieving Data from Map

Values are retrieved by their keys from Map objects using the .get() method.

console.log(fruits.get('Apples')); // Output: 5
console.log(fruits.get('Oranges')); // Output: 8

This retrieves the information that there are 5 apples and 8 oranges in the store.

Determining Whether Keys are in Map

Checking whether a key is in a Map object can be done using the .has() method.

console.log(fruits.has('Apples')); // Output: true
console.log(fruits.has('Bananas')); // Output: false

The first statement checks that there are apples in fruits, while the second statement finds that there are no bananas in fruits and returns false.

Retrieving the Size of a Map

The number of keys in a Map object can be checked using the .size property.

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

There are 2 key-value pairs in fruits: 'Apples' : 5 and 'Oranges' : 8.

Removing Data from Map

Data can be removed from Map using the .delete() method.

console.log(fruits.delete('Oranges')); // Output: true
console.log(fruits.delete('Strawberries')); // Output: false

The first statement returns true because fruits contain Oranges as a key and has removed it. The second statement returns false because Strawberries is not a key in fruits.

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