Use static fields and properties from NodeJs package in C# app

This article provides an introduction to cross-technology handling of static fields and properties.
Javonet allows you to reference and use modules or packages written in (Java/Kotlin/Groovy/Clojure, C#/VB.NET, Ruby, Perl, Python, JavaScript/TypeScript) like they were created in your technology. If have not yet created your first project check Javonet overview and quick start guides for your technology.

With Javonet you can interact with static field and properties from NodeJs package like they were available in C# but invocation must be performed through Javonet SDK API.

Custom NodeJs package with static fields and properties

With Javonet it is possible to reference any custom NodeJs package and interact with public static fields and properties declared on types defined within that module almost the same as with any other C# library.

Snippet below represents the sample code from NodeJs package which contains class with fields:

const fs = require('fs').promises;

class TestClass {

    publicValue;
    #privateValue;
    static staticValue = 3;
    
    constructor(first, second) {
    	this.publicValue = first;
    	this.#privateValue = second;
    }
}

module.exports = TestClasspublicValue;
#privateValue;
static staticValue = 3;

constructor(first, second) {
	this.publicValue = first;
	this.#privateValue = second;
}

It is possible to get one of the declared static fields from NodeJs package using following C# code.

namespace SampleProgram {
	using Javonet.Netcore.Sdk;
	internal class Program {
		private static string resourcesDirectory = ".";
		static void Main(string[] args) {

			// use Activate only once in your app
			Javonet.Activate("your-license-key");
			
			// create called runtime context
			var calledRuntime = Javonet.InMemory().Nodejs();
			
			// set up variables
			string libraryPath = resourcesDirectory + "/TestClass.js";
			string className = "TestClass";
			
			// load custom library
			calledRuntime.LoadLibrary(libraryPath);
			
			// get type from the runtime
			var calledRuntimeType = calledRuntime.GetType(className).Execute();
			
			// get type's static field
			var response = calledRuntimeType.GetStaticField("staticValue").Execute();
			
			// get value from response
			var result = (int)response.GetValue();
			
			// write result to console
			System.Console.WriteLine(result);
		}
	}
}const fs = require('fs').promises;

class TestClass {

    publicValue;
    #privateValue;
    static staticValue = 3;
    
    constructor(first, second) {
    	this.publicValue = first;
    	this.#privateValue = second;
    }
}

module.exports = TestClass// use Activate only once in your app
Javonet.Activate("your-license-key");

// create called runtime context
var calledRuntime = Javonet.InMemory().Nodejs();

// set up variables
string libraryPath = resourcesDirectory + "/TestClass.js";
string className = "TestClass";

// load custom library
calledRuntime.LoadLibrary(libraryPath);

// get type from the runtime
var calledRuntimeType = calledRuntime.GetType(className).Execute();

// get type's static field
var response = calledRuntimeType.GetStaticField("staticValue").Execute();

// get value from response
var result = (int)response.GetValue();

// write result to console
System.Console.WriteLine(result);

This uses in memory runtime bridging to load the NodeJs package, and next retrieves reference to specific type and gets the static field. Result of the invocation is returned as regular C# value and can be used for further processing. It is possible to set one of the declared static fields from NodeJs package using following C# code.

namespace SampleProgram {
	using Javonet.Netcore.Sdk;
	internal class Program {
		private static string resourcesDirectory = ".";
		static void Main(string[] args) {

			// use Activate only once in your app
			Javonet.Activate("your-license-key");
			
			// create called runtime context
			var calledRuntime = Javonet.InMemory().Nodejs();
			
			// set up variables
			string libraryPath = resourcesDirectory + "/TestClass.js";
			string className = "TestClass";
			
			// load custom library
			calledRuntime.LoadLibrary(libraryPath);
			
			// get type from the runtime
			var calledRuntimeType = calledRuntime.GetType(className).Execute();
			
			// set static field's value
			calledRuntimeType.SetStaticField("staticValue", 75).Execute();
			
			// get type's static field
			var response = calledRuntimeType.GetStaticField("staticValue").Execute();
			
			// get value from response
			var result = (int)response.GetValue();
			
			// write result to console
			System.Console.WriteLine(result);
		}
	}
}const fs = require('fs').promises;

class TestClass {

    publicValue;
    #privateValue;
    static staticValue = 3;
    
    constructor(first, second) {
    	this.publicValue = first;
    	this.#privateValue = second;
    }
}

module.exports = TestClass// use Activate only once in your app
Javonet.Activate("your-license-key");

// create called runtime context
var calledRuntime = Javonet.InMemory().Nodejs();

// set up variables
string libraryPath = resourcesDirectory + "/TestClass.js";
string className = "TestClass";

// load custom library
calledRuntime.LoadLibrary(libraryPath);

// get type from the runtime
var calledRuntimeType = calledRuntime.GetType(className).Execute();

// set static field's value
calledRuntimeType.SetStaticField("staticValue", 75).Execute();

// get type's static field
var response = calledRuntimeType.GetStaticField("staticValue").Execute();

// get value from response
var result = (int)response.GetValue();

// write result to console
System.Console.WriteLine(result);

This uses in memory runtime bridging to load the NodeJs package, and next retrieves reference to specific type, then sets and gets the static field. Result of the invocation is returned as regular C# value and can be used for further processing.

Framework static fields and properties

The same steps are required to get types and fields from framework NodeJs package:

namespace SampleProgram {
	using Javonet.Netcore.Sdk;
	internal class Program {
		private static string resourcesDirectory = ".";
		static void Main(string[] args) {

			// use Activate only once in your app
			Javonet.Activate("your-license-key");
			
			// create called runtime context
			var calledRuntime = Javonet.InMemory().Nodejs();
			
			// get type from the runtime
			var calledRuntimeType = calledRuntime.GetType("Math").Execute();
			
			// get type's static field
			var response = calledRuntimeType.GetStaticField("PI").Execute();
			
			// get value from response
			var result = (double)response.GetValue();
			
			// write result to console
			System.Console.WriteLine(result);
		}
	}
}const fs = require('fs').promises;

class TestClass {

    // empty
}

module.exports = TestClass// use Activate only once in your app
Javonet.Activate("your-license-key");

// create called runtime context
var calledRuntime = Javonet.InMemory().Nodejs();

// get type from the runtime
var calledRuntimeType = calledRuntime.GetType("Math").Execute();

// get type's static field
var response = calledRuntimeType.GetStaticField("PI").Execute();

// get value from response
var result = (double)response.GetValue();

// write result to console
System.Console.WriteLine(result);

The same operation can be performed remotely by just changing the new Runtime Context invocation from in memory to tcp that will create and interact with your NodeJs package objects on any remote node, container or service that hosts Javonet Code Gateway. This way you can preserve the same logic in your application and instantly switch between monolithic and microservices architecture without the need to implement the integration layer based on web services or other remote invocation methods.

Read more about use cases and software architecture scenarios where Javonet runtime bridging technology can support your development process.

Use static fields and properties from NodeJs package in C# app

Custom NodeJs package with static fields and properties

Framework static fields and properties

Additional references