Node.js vm.isContext() Method

The vm.isContext() method is an inbuilt application programming interface of the vm module which is used to check if the stated object is being contextified using vm.createContext() method or not.

Syntax:

vm.isContext( object )

Parameters: This method accepts single parameter object.

Return Value: It returns true if the stated object is being contextified else it returns false.

Below examples illustrate the use of vm.isContext() method in Node.js:

Example 1:

javascript

// Node.js program to demonstrate the
// vm.isContext() method

// Including util and vm module
const util = require('util');
const vm = require('vm');

// Assigning value to the global variable
global.globalVar = 7;

// Defining Context object
const object = { globalVar: 3 };

// Contextifying stated object
// using createContext method
vm.createContext(object);

// Compiling code
vm.runInContext('globalVar *= 6;', object);

// Displays the context
console.log(object);

// Displays value of global variable
console.log(global.globalVar);

// Calling isContext method
vm.isContext(object);

Output:

{ globalVar: 18 }
7
true

Here, globalVar in the context is 18 in output as (6*3 = 18) but the value of globalVar is still 7. Moreover, here the stated object is being contextified so true is returned.

Example 2:

javascript

// Node.js program to demonstrate the
// vm.isContext() method

// Including util and vm module
const util = require('util');
const vm = require('vm');

// Assigning value to the global variable
global.globalVar = 7;

// Defining Context object
const object = { globalVar: 3 };

// Displays the context
console.log(object);

// Displays value of global variable
console.log(global.globalVar);

// Calling isContext method
vm.isContext(object);

Output:

{ globalVar: 3 }
7
false

Here, the stated object is not contextified so, false is returned.

Reference: https://nodejs.org/api/vm.html#vm_vm_iscontext_object