Node.js util.types.isAsyncFunction() Method

The util.types.isAsyncFunction() method is an inbuilt application programming interface of the util module which is used to type check for asynchronous functions in the node.js.
Syntax:

util.types.isAsyncFunction( value )

Parameters: This method accepts single parameter as mentioned above and described below: 

• value: It is a required parameter that holds any datatype.

Return Value: It returns a boolean value, TRUE if the value is an async function from the perspective of the JavaScript engine, FALSE otherwise.
Below examples illustrate the use of util.types.isAsyncFunction() method in Node.js:
Example 1:

javascript

// Node.js program to demonstrate the
// util.types.isAsyncFunction() Method

// Allocating util module
const util = require('util');

// Functions to be passed as parameter of
// util.types.isAsyncFunction() method
var f2 = async function function2(){}
var f1 = function function1(){}

// Printing the returned value from
// util.types.isAsyncFunction() method
console.log(util.types.isAsyncFunction(f2));
console.log(util.types.isAsyncFunction(f1));

Output:

true
false

Example 2:

javascript

// Node.js program to demonstrate the
// util.types.isAsyncFunction() Method

// Allocating util module
const util = require('util');

// Functions to be passed as parameter
var f2 = async function function2() { }
var f1 = function function1() { }

// Calling util.types.isAsyncFunction() method
if (util.types.isAsyncFunction(f2))
    console.log("The passed value is an Async function.");
else
    console.log("The passed value is not an Async function");

if (util.types.isAsyncFunction(f1))
    console.log("The passed value is an Async function.");
else
    console.log("The passed value is not an Async function");

Output:

The passed value is an Async function.
The passed value is not an Async function

Note: The above program will compile and run by using the node filename.js command.
Reference: https://nodejs.org/api/util.html#util_util_types_isasyncfunction_value