How to Get the Size (Number of Key-Value Pairs) of a Map in JavaScript

How to Get the Size (Number of Key-Value Pairs) of a Map in JavaScript ?

Answer

To get the size (number of key-value pairs) of a map in JavaScript, you can use the size property. This property returns the number of elements in the map.

✐ Examples

1 Getting the Size of a Map Using size Property

We can get the size of a map in JavaScript using the size property, which provides the number of key-value pairs in the map.

For example,

We start by declaring and initializing a map named myMap with some key-value pairs. In this example, the map has string keys and integer values.
We use the size property to get the number of key-value pairs in the map.
We store the size in a variable named mapSize.
We print the size to the console using the console.log function to verify the number of key-value pairs in the map.

JavaScript Program

const myMap = new Map([
    ['one', 1],
    ['two', 2],
    ['three', 3]
]);

// Get the size of the map
const mapSize = myMap.size;

// Print the size
console.log('Size of the map:', mapSize);

Output

Size of the map: 3

2 Getting the Size of an Empty Map

We can also get the size of an empty map in JavaScript using the size property, which returns 0 when the map is empty.

For example,

We start by declaring an empty map named emptyMap with string keys and integer values.
We use the size property to get the number of key-value pairs in the empty map.
We store the size in a variable named emptyMapSize.
We print the size to the console using the console.log function to verify that the map is empty.

JavaScript Program

const emptyMap = new Map();

// Get the size of the empty map
const emptyMapSize = emptyMap.size;

// Print the size
console.log('Size of the empty map:', emptyMapSize);

Output

Size of the empty map: 0

3 Getting the Size of a Map After Adding Elements

We can get the size of a map in JavaScript after adding elements using the size property, which provides the updated number of key-value pairs in the map.

For example,

We start by declaring an empty map named dynamicMap with string keys and integer values.
We add some key-value pairs to the map using the map's set method.
We use the size property to get the number of key-value pairs in the map after adding elements.
We store the size in a variable named dynamicMapSize.
We print the size to the console using the console.log function to verify the updated number of key-value pairs in the map.

JavaScript Program

const dynamicMap = new Map();

// Add elements to the map
dynamicMap.set('one', 1);
dynamicMap.set('two', 2);
dynamicMap.set('three', 3);

// Get the size of the map after adding elements
const dynamicMapSize = dynamicMap.size;

// Print the size
console.log('Size of the map after adding elements:', dynamicMapSize);

Output

Size of the map after adding elements: 3

Summary

In this tutorial, we learned How to Get the Size (Number of Key-Value Pairs) of a Map in JavaScript language with well detailed examples.

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How to Get the Size (Number of Key-Value Pairs) of a Map in JavaScript