method

vm.Script.runInNewContext

contextObject?: number | Context,
options?: RunningScriptInNewContextOptions
): any;

This method is a shortcut to script.runInContext(vm.createContext(options), options). 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 a vm.Script
  4. Runs the compiled 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 code that sets a global variable, then executes the code multiple times in different contexts. The globals are set on and contained within each individual context.

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

const script = new Script('globalVar = "set"');

const contexts = [{}, {}, {}];
contexts.forEach((context) => {
  script.runInNewContext(context);
});

console.log(contexts);
// Prints: [{ globalVar: 'set' }, { globalVar: 'set' }, { globalVar: 'set' }]

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

  • 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.

  • 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.

  • 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.