Node.js vm.createContext() Method

Last Updated : 3 Jun, 2026

The vm.createContext() method creates a separate execution context for running one or more scripts. If no contextObject is provided, it returns a new empty contextified object.

  • If an object is provided, it becomes the global object inside scripts executed with vm.runInContext() or script.runInContext().
  • Changes inside the context do not affect actual global variables outside the VM context.

Syntax

vm.createContext( contextObject, options )

Parameters 

  • contextObject: It is the object which is contextified.
  • options: It is optional and returns Object.

Return Value: It returns contextified JS object.

Use cases of vm.createContext()

  • Running untrusted JavaScript code safely in an isolated environment.
  • Creating separate execution environments with their own variables and global objects.
  • Testing or sandboxing scripts without affecting the main Node.js application state.

Example 1: Creating an isolated execution context using vm.createContext() where changes to globalVar affect only the context object, not the actual global variable.

JavaScript 
// Node.js program to demonstrate the     
// vm.createContext([contextObject[, options]])
// method
 
// Including util and vm module
const util = require('util');
const vm = require('vm');
 
// Assigning value to the global variable
global.globalVar = 10;
 
// Defining Context object
const object = { globalVar: 4 };
 
// Contextifying stated object
// using createContext method
vm.createContext(object);
 
// Compiling code
vm.runInContext('globalVar /= 2;', object);
 
// Displays the context
console.log("Context: ", object);
 
// Displays value of global variable
console.log("Global Variable is ", global.globalVar);

Output: 

Context:  { globalVar: 2 }
Global Variable is  10

Here, globalVar in the context is 2 in output as (4/2 = 2) but the value of globalVar is still 10. 

Example 2: Modifying variables inside a separate VM context using vm.createContext(), without changing the actual global variable.

JavaScript 
// Node.js program to demonstrate the     
// vm.createContext([contextObject[, options]])
// method
 
// Including util and vm module
const util = require('util');
const vm = require('vm');
 
// Assigning value to the global variable
global.globalVar = 5;
 
// Defining Context object
const object = { globalVar: 20 };
 
// Contextifying stated object
// using createContext method
vm.createContext(object);
 
// Compiling code
vm.runInContext('globalVar += 2;', object);
 
// Displays the context
console.log("Context: ", object);
 
// Displays value of global variable
console.log("Global Variable is ", global.globalVar);

Output: 

Context:  { globalVar: 22 }
Global Variable is  5

Here, globalVar in the context is 22 in output as (20+2 = 22) but the value of globalVar is still 5. 

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

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