Implementation:Nightwatchjs Nightwatch Custom Command Type Definitions

Knowledge Sources	Nightwatchjs_Nightwatch Custom Commands
Domains	Testing, Type_System, Extensibility
Last Updated	2026-02-12 00:00 GMT

Overview

TypeScript type definitions for the `NightwatchCustomCommandsModel` interface used to create custom commands, and the `NightwatchCustomCommands` augmentation interface.

Description

The custom-command.d.ts file defines:

CustomCommandInstance — Extends `CommandInstance` from the core types, providing the base class for custom command instances.
NightwatchCustomCommandsModel — The interface for custom command classes. Requires a `command(...args)` method that returns `unknown | Promise<unknown>`.
NightwatchCustomCommands — Empty augmentation interface that users extend via module declaration to register custom commands on the `browser` object.

Usage

Implement `NightwatchCustomCommandsModel` when creating class-based custom commands. Augment `NightwatchCustomCommands` to add TypeScript types for custom commands accessible on `browser`.

Code Reference

Source Location

Repository: Nightwatchjs_Nightwatch
File: types/custom-command.d.ts
Lines: 1-25

Signature

export interface CustomCommandInstance extends CommandInstance {}

export interface NightwatchCustomCommandsModel {
  command: (...args: any[]) => unknown | Promise<unknown>;
}

export interface NightwatchCustomCommands {}

Import

import { NightwatchCustomCommandsModel } from 'nightwatch';

I/O Contract

Inputs

Name	Type	Required	Description
command	function	Yes	The method implementing the custom command logic
args	any[]	No	Arguments passed when invoking the command

Outputs

Name	Type	Description
Return value	unknown / Promise	Command result, can be synchronous or async
Registered on browser	Method	Custom command available as `browser.customName()`

Usage Examples

Class-Based Custom Command

import { NightwatchCustomCommandsModel } from 'nightwatch';

class LogMessage implements NightwatchCustomCommandsModel {
  async command(message: string) {
    console.log(`[Custom] ${message}`);
    return Promise.resolve();
  }
}

export default LogMessage;

Augmenting TypeScript Types

declare module 'nightwatch' {
  interface NightwatchCustomCommands {
    logMessage(message: string): this;
  }
}

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