Node.js util.types.isMapIterator() Method

The util.types.isMapIterator() method is an inbuilt application programming interface of util module which is primarily designed to support the needs of Node.js internal APIs.

The util.types.isMapIterator() method is used to determine whether the value is an iterator returned for a built-in Map instance or not.

Syntax:

util.types.isMapIterator( value )

Parameters: This method accepts a single parameters value which holds any valid JavaScript data types like Boolean, Null, Number, Object, etc.

Return value: It returns a Boolean value i.e. returns true if value is an iterator returned for a built-in Map otherwise it returns false.

Below examples illustrate the use of util.types.isMapIterator() Method in Node.js:

Example 1:

// Node.js program to demonstrate the
// util.types.isMapIterator() method

// Using require to access util module
const util = require('util');

// Using util.types.isMapIterator() method
console.log(util.types.isMapIterator(true));

// Using util.types.isMapIterator() method
console.log(util.types.isMapIterator(new Map().values()));

// Using util.types.isMapIterator() method
console.log(util.types.isMapIterator(new Map().keys()));

Output:

false
true
true

Example 2:

// Node.js program to demonstrate the
// util.types.isMapIterator() method

// Using require to access util module
const util = require('util');

const map = new Map();

// Using util.types.isMapIterator() method
console.log(util.types.isMapIterator(map.keys()));

// Using util.types.isMapIterator() method
console.log(util.types.isMapIterator(map.entries()));

// Using util.types.isMapIterator() method
console.log(util.types.isMapIterator(map[Symbol.iterator]()));

Output:

true
true
true

Note: The above program will compile and run by using the node index.js command.

Reference: https://nodejs.org/dist/latest-v13.x/docs/api/util.html#util_util_types_ismapiterator_value