How to get the size of a Map in JavaScript?

JavaScript Get Size of Map

To get the size of a Map in JavaScript, access size property of this Map. size is a read only property of Map object and returns an integer value representing the number of key-value pairs in this Map.

Syntax

The syntax to access size property on the Map map is

map.size;

Examples

In the following example, we take a Map with two items and find the size of this Map programmatically using size property.

index.html

<!DOCTYPE html>
<html lang="en">
<body>
    <pre id="output"></pre>
    <script>
        var map1 = new Map([
            ['a', 10],
            ['b', 20]
        ]);

        var mapSize = map1.size;

        var displayOutput = 'Size of map is ' + mapSize + '.';
        document.getElementById('output').innerHTML += displayOutput;
    </script>
</body>
</html>

The size of an empty map is zero.

index.html

<!DOCTYPE html>
<html lang="en">
<body>
    <pre id="output"></pre>
    <script>
        var map1 = new Map();

        var mapSize = map1.size;

        var displayOutput = 'Size of map is ' + mapSize + '.';
        document.getElementById('output').innerHTML += displayOutput;
    </script>
</body>
</html>

Conclusion

In this JavaScript Tutorial, we learned how to get the size of a Map in JavaScript using size property, with examples.