Node.js util.types.isExternal()方法

util.types.isExternal()方法是util模块内置的应用程序编程接口，用于检查值是否是node.js中的本机外部值。

语法：

util.types.isExternal( value )

参数： 该方法接受一个参数，如上所述并以下面的方式进行描述。

• value： 这是任意数据类型的必需参数。

返回值： 如果该值是原生外部值，则返回真，否则返回假。

以下示例演示了在Node.js中使用util.types.isExternal()方法：

示例1：

// 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')));

输出:

false
true
false
false

示例2：

// 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.");

输出：

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.

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