Node.js util.types.isExternal() Method

The util.types.isExternal() method is an inbuilt application programming interface of the util module which is used to check if the value is a native External value in the node.js.

Syntax: 

util.types.isExternal( value )

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

• value: It is a required parameter of any datatype.

Return Value: This returns a boolean value, TRUE if the value is a native External value, FALSE otherwise.

 The below examples illustrate the use of util.types.isExternal() method in Node.js:

Example 1:

Javascript

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

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

// Value to be passed as parameter
// of util.types.isExternal() method
const v1 = new Date();
const { JSStream } = process.binding('js_stream');
const external = (new JSStream())._externalStream;

// Printing the returned value from
// util.types.isExternal() method

console.log(util.types.isExternal(v1));
console.log(util.types.isExternal(external));
console.log(util.types.isExternal(0));
console.log(util.types.isExternal(new String('foo')));

Output:

false
true
false
false

Example 2:

Javascript

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

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

// Value to be passed as parameter
// of util.types.isExternal() method
const v1 = new Date();
const { JSStream } = process.binding('js_stream');
const ext = (new JSStream())._externalStream;
const str = new String('Geeks')

// Calling
// util.types.isExternal() method
if (util.types.isExternal(v1))
    console.log("It is a native External value.");
else
    console.log("It is not a native External value.");

if (util.types.isExternal(ext))
    console.log("It is a native External value.");
else
    console.log("It is not a native External value.");

if (util.types.isExternal(0))
    console.log("It is a native External value.");
else
    console.log("It is not a native External value.");

if (util.types.isExternal(str))
    console.log("It is a native External value.");
else
    console.log("It is not a native External value.");

Output:

It is not a native External value.
It is a native External value.
It is not a native External value.
It is not a native External value.

Reference: https://nodejs.org/api/util.html#util_util_types_isexternal_value