function

vm.runInNewContext

function runInNewContext(
code: string,
contextObject?: number | Context,
options?: string | RunningCodeInNewContextOptions
): any;

This method is a shortcut to (new vm.Script(code, options)).runInContext(vm.createContext(options), options). If options is a string, then it specifies the filename.

It does several things at once:

  1. Creates a new context.
  2. If contextObject is an object, contextifies it with the new context. If contextObject is undefined, creates a new object and contextifies it. If contextObject is vm.constants.DONT_CONTEXTIFY, don't contextify anything.
  3. Compiles the code as avm.Script
  4. Runs the compield code within the created context. The code does not have access to the scope in which this method is called.
  5. Returns the result.

The following example compiles and executes code that increments a global variable and sets a new one. These globals are contained in the contextObject.

import { runInNewContext, constants } from 'node:vm';

const contextObject = {
  animal: 'cat',
  count: 2,
};

runInNewContext('count += 1; name = "kitty"', contextObject);
console.log(contextObject);
// Prints: { animal: 'cat', count: 3, name: 'kitty' }

// This would throw if the context is created from a contextified object.
// vm.constants.DONT_CONTEXTIFY allows creating contexts with ordinary global objects that
// can be frozen.
const frozenContext = runInNewContext(
  'Object.freeze(globalThis); globalThis;',
  constants.DONT_CONTEXTIFY,
);
@param code

The JavaScript code to compile and run.

@param contextObject

Either vm.constants.DONT_CONTEXTIFY or an object that will be contextified. If undefined, an empty contextified object will be created for backwards compatibility.

@returns

the result of the very last statement executed in the script.

Referenced types

interface Context

interface RunningCodeInNewContextOptions

  • breakOnSigint?: boolean

    If true, the execution will be terminated when SIGINT (Ctrl+C) is received. Existing handlers for the event that have been attached via process.on('SIGINT') will be disabled during script execution, but will continue to work after that. If execution is terminated, an Error will be thrown.

  • cachedData?: ArrayBufferView<ArrayBufferLike>

    Provides an optional data with V8's code cache data for the supplied source.

  • columnOffset?: number

    Specifies the column number offset that is displayed in stack traces produced by this script.

  • contextCodeGeneration?: { strings: boolean; wasm: boolean }
  • contextName?: string

    Human-readable name of the newly created context.

  • contextOrigin?: string

    Origin corresponding to the newly created context for display purposes. The origin should be formatted like a URL, but with only the scheme, host, and port (if necessary), like the value of the url.origin property of a URL object. Most notably, this string should omit the trailing slash, as that denotes a path.

  • displayErrors?: boolean

    When true, if an Error occurs while compiling the code, the line of code causing the error is attached to the stack trace.

  • filename?: string

    Specifies the filename used in stack traces produced by this script.

  • importModuleDynamically?: number | DynamicModuleLoader<Script>

    Used to specify how the modules should be loaded during the evaluation of this script when import() is called. This option is part of the experimental modules API. We do not recommend using it in a production environment. For detailed information, see Support of dynamic import() in compilation APIs.

  • lineOffset?: number

    Specifies the line number offset that is displayed in stack traces produced by this script.

  • microtaskMode?: 'afterEvaluate'

    If set to afterEvaluate, microtasks will be run immediately after the script has run.

  • timeout?: number

    Specifies the number of milliseconds to execute code before terminating execution. If execution is terminated, an Error will be thrown. This value must be a strictly positive integer.