Implementation:Microsoft Playwright Server JavaScript

Knowledge Sources	Microsoft_Playwright
Domains	JavaScript Execution, Remote Object Handling
Last Updated	2026-02-12 00:00 GMT

Overview

Concrete tool for managing JavaScript execution contexts and object handles on the server side provided by the Playwright library.

Description

The `javascript.ts` module provides the `ExecutionContext` and `JSHandle` classes that form the foundation for JavaScript evaluation across all browser engines. The `ExecutionContext` class (extending `SdkObject`) manages a utility script instance, delegates evaluation to browser-specific `ExecutionContextDelegate` implementations, and handles context destruction. The `JSHandle` class represents a reference to a JavaScript object in the browser, supporting property access, JSON serialization, evaluation on the object, and disposal. The module defines generic function types (`Func0`, `Func1`, `FuncOn`) for type-safe evaluation and uses `SmartHandle<T>` to automatically return `ElementHandle` for DOM nodes. The utility script provides common operations injected into the browser.

Usage

Use this module as the base for all JavaScript evaluation operations in the Playwright server. Browser-specific implementations (CRExecutionContext, FFExecutionContext, etc.) extend these abstractions.

Code Reference

Source Location

• Repository: Microsoft_Playwright
• File: packages/playwright-core/src/server/javascript.ts

Signature

export interface ExecutionContextDelegate {
  rawEvaluateJSON(expression: string): Promise<any>;
  rawEvaluateHandle(context: ExecutionContext, expression: string): Promise<JSHandle>;
  evaluateWithArguments(expression: string, returnByValue: boolean, utilityScript: JSHandle, values: any[], handles: JSHandle[]): Promise<any>;
  getProperties(object: JSHandle): Promise<Map<string, JSHandle>>;
  releaseHandle(handle: JSHandle): Promise<void>;
}

export class ExecutionContext extends SdkObject {
  readonly delegate: ExecutionContextDelegate;
  readonly worldNameForTest: string;

  constructor(parent: SdkObject, delegate: ExecutionContextDelegate, worldNameForTest: string);
  async evaluateExpression(expression: string, options: { isFunction?: boolean }, arg?: any): Promise<any>;
  async evaluateExpressionHandle(expression: string, options: { isFunction?: boolean }, arg?: any): Promise<JSHandle>;
}

export class JSHandle<T = any> {
  readonly _context: ExecutionContext;

  async evaluate<R>(pageFunction: FuncOn<T, any, R>, arg?: any): Promise<R>;
  async evaluateHandle<R>(pageFunction: FuncOn<T, any, R>, arg?: any): Promise<SmartHandle<R>>;
  async getProperty(name: string): Promise<JSHandle>;
  async jsonValue(): Promise<T>;
  async dispose(): Promise<void>;
}

Import

import { ExecutionContext, JSHandle } from '../server/javascript';
import type { ExecutionContextDelegate, Func0, Func1, FuncOn, SmartHandle } from '../server/javascript';

I/O Contract

Inputs

Name	Type	Required	Description
parent	SdkObject	Yes	Parent SDK object for instrumentation
delegate	ExecutionContextDelegate	Yes	Browser-specific evaluation delegate
worldNameForTest	string	Yes	World identifier (main, utility, content-script)
expression	string	Yes	JavaScript expression or function to evaluate
arg	any	No	Argument to pass to the evaluated function

Outputs

Name	Type	Description
evaluation result	any	Deserialized result of JavaScript evaluation
JSHandle	JSHandle	Handle to a JavaScript object in the browser
properties	Map<string, JSHandle>	Object properties as a map of handles
jsonValue	T	JSON-serializable value of the handle

Usage Examples

// Browser-specific context creation
const context = new ExecutionContext(parentSdkObject, crDelegate, 'main');

// Evaluate expression
const title = await context.evaluateExpression('document.title', { isFunction: false });

// Get handle
const handle = await context.evaluateExpressionHandle('document.body', { isFunction: false });

// Work with handle
const tagName = await handle.evaluate(el => el.tagName);
const props = await handle.getProperties('childNodes');
await handle.dispose();

Related Pages

• Environment:Microsoft_Playwright_Node_Runtime_Environment