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Neutralinojs offers the extensions API to write custom backend code with any programming language, but extensions come with the following drawbacks that affect apps in several scenarios:

  • Extensions use a shared WebSocket for communication, so using direct C++ references (i.e., the window handler) is impossible within extensions.
  • The developer is responsible for packaging their extension binaries.
  • A C++-based extension is not fast as native C++-based code due to the WebSockets-based IPC.

Alternatively, a developer can download the framework C++ code, modify it, and re-compile it. But, the developer may face issues while synching upstream code modifications. So, Neutralinojs offers a separate namespace, a generic JavaScript function template, pre-developed helper functions for handling JavaScript-to-C++ parameter mapping (i.e., helpers::hasField(json, '<fieldname>')), and a developer guide to add custom APIs to the Neutralinojs framework without updating the framework core.


Returns all custom methods added by the app developer.

Return Array (awaited):

A string array of all custom method identifiers.

let methods = await Neutralino.custom.getMethods();

custom.add(num1, num2, options)


This is a sample method and official Neutralinojs framework builds don't include this method by default. So, you have to download the Neutralinojs framework source code and uncomment the add method in the custom namespace and router.cpp.

This method returns the sum of two numbers for demonstration purposes of custom methods.


  • num1 Number: The first number for the summation process.
  • num2 Number: The second number for the summation process.


  • addExtraFive Boolean: Adds extra five to the numerical result.
  • addExtraTen Boolean: Adds extra ten to the numerical result.

Return Number (awaited):

The sum of input numerical parameters with extra value additions based on options.

let sum;
sum = await Neutralino.custom.add(10, 10); // 20
sum = await Neutralino.custom.add(1, 1, { addExtraFive: true, addExtraTen: true }); // 17

Check the add method implementation and learn how to capture, validate, and process parameters in C++. For compiling your Neutralinojs fork, you can use the existing GitHub Actions workflows.