JavaScript Map has()
Syntax & Examples

Map.has() method

The has() method of the Map object in JavaScript returns a boolean indicating whether a value has been associated with the passed key in the Map object or not.

Syntax of Map.has()

The syntax of Map.has() method is:

has(key)

This has() method of Map returns a boolean indicating whether a value has been associated with the passed key in the Map object or not.

Parameters

ParameterOptional/RequiredDescription
keyrequiredThe key of the element to test for presence in the Map.

Return Type

Map.has() returns value of type boolean.


✐ Examples

1 Using has() to check for a key in a Map

In JavaScript, we can use the has() method to check if a specific key is present in a Map object.

For example,

  1. Create a new Map object map with initial key-value pairs.
  2. Use the has() method to check if the key 'a' is present in the map.
  3. Log the result to the console using console.log().

JavaScript Program

const map = new Map([['a', 1], ['b', 2]]);
const hasA = map.has('a');
console.log(hasA);

Output

true

2 Using has() to check for a non-existent key

In JavaScript, we can use the has() method to check if a key that is not present in the Map object returns false.

For example,

  1. Create a new Map object map with initial key-value pairs.
  2. Use the has() method to check if the key 'c' is present in the map.
  3. Log the result to the console using console.log().

JavaScript Program

const map = new Map([['a', 1], ['b', 2]]);
const hasC = map.has('c');
console.log(hasC);

Output

false

3 Using has() with a Map of objects

In JavaScript, we can use the has() method to check if an object key is present in a Map object.

For example,

  1. Create a new Map object map with initial key-value pairs where keys are objects.
  2. Use the has() method to check if a specific object key is present in the map.
  3. Log the result to the console using console.log().

JavaScript Program

const key1 = { id: 1 };
const key2 = { id: 2 };
const map = new Map([
  [key1, 'value1'],
  [key2, 'value2']
]);
const hasKey1 = map.has(key1);
console.log(hasKey1);

Output

true

Summary

In this JavaScript tutorial, we learned about has() method of Map: the syntax and few working examples with output and detailed explanation for each example.