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Add custom RPC methods

Introduction

Web3.js is a popular library for interacting with the Ethereum blockchain. It provides a set of APIs to interact with Ethereum nodes via JSON-RPC calls. For adding new JSON-RPC function calls to the library, you can do so using the plugin feature in web3.js 4.x. This allows you to extend the functionality of Web3.js and add support for new JSON-RPC methods.

:::caution In Web3.js 1.x, web3.extend() function could be used to add new JSON-RPC methods. web3.extend() is also available in Web3 v4.0.4+ with some breaking changes. However it is recommended to use Web3 Plugin feature for extending web3 functionality if you are developing new feature. Read the "Extending Web3.js" guide to learn more about the legacy web3.extend() method. :::

Following tutorial will guide you through the process of creating a custom plugin to extend the functionality of web3.js 4.x and add support for new RPC methods.

Creating new RPC methods Plugin in 4 Steps

Step 1: Setting Up Web3.js as a Peer Dependency and Creating a TypeScript Class

First add web3.js as peer dependency in project´s package.json and create a TypeScript class for your plugin. This class should extend the Web3Plugin class provided by web3.js.

:::info This will give your plugin access to requestManager and accountProvider. :::

javascript

const { Web3PluginBase } = require('web3');

//highlight-start
class CustomRpcMethodsPlugin extends Web3PluginBase {
	// step 1
	// ...
}
//highlight-end

module.exports = CustomRpcMethodsPlugin;

</TabItem>

typescript

import { Web3PluginBase } from 'web3';

//highlight-start
export default class CustomRpcMethodsPlugin extends Web3PluginBase {
	// step 1
	// ...
}
//highlight-end

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Step 2: Adding a Public `pluginNamespace` Property to the Plugin Class

After that add public pluginNamespace property. This will be used to access your plugin, as mentioned in step number 5 code example.

javascript

const { Web3PluginBase } = require('web3');

class CustomRpcMethodsPlugin extends Web3PluginBase {
	//highlight-start
	pluginNamespace = 'customRpcMethods'; // step 2
	//highlight-end
}

module.exports = CustomRpcMethodsPlugin;

</TabItem>

typescript

import { Web3PluginBase } from 'web3';

export default class CustomRpcMethodsPlugin extends Web3PluginBase {
	//highlight-start
	public pluginNamespace = 'customRpcMethods'; // step 2
	//highlight-end
}

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Step 3: Creating Custom RPC Methods in the Plugin Class

Once plugin class is created using above mentioned steps, its very easy to add new RPC methods like:

javascript

const { Web3PluginBase } = require('web3');

class CustomRpcMethodsPlugin extends Web3PluginBase {
	pluginNamespace = 'customRpcMethods';

	//highlight-start
	async customRpcMethod() {
		// step 3
		return this.requestManager.send({
			// plugin has access to web3.js internal features like request manager
			method: 'custom_rpc_method',
			params: [],
		});
	}
	//highlight-end
}

module.exports = CustomRpcMethodsPlugin;

</TabItem>

typescript

import { Web3PluginBase } from 'web3';

export default class CustomRpcMethodsPlugin extends Web3PluginBase {
	public pluginNamespace = 'customRpcMethods';

	//highlight-start
	public async customRpcMethod() {
		// step 3
		return this.requestManager.send({
			// plugin has access to web3.js internal features like request manager
			method: 'custom_rpc_method',
			params: [],
		});
	}
	//highlight-end
}

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Step 4: Enabling Access to the Plugin on the Web3 Object

(For TypeScript) Final step is setting up module augmentation, this will allow you to access plugin on web3 object.

javascript

const { Web3PluginBase } = require('web3');

class CustomRpcMethodsPlugin extends Web3PluginBase {
	pluginNamespace = 'customRpcMethods';

	async customRpcMethod() {
		return this.requestManager.send({
			// plugin has access to web3.js internal features like request manager
			method: 'custom_rpc_method',
			params: [],
		});
	}
}

module.exports = CustomRpcMethodsPlugin;

</TabItem>

typescript

import { Web3PluginBase } from 'web3';

export default class CustomRpcMethodsPlugin extends Web3PluginBase {
	public pluginNamespace = 'customRpcMethods';

	public async customRpcMethod() {
		return this.requestManager.send({
			// plugin has access to web3.js internal features like request manager
			method: 'custom_rpc_method',
			params: [],
		});
	}
}

//highlight-start
// Module Augmentation
declare module 'web3' {
	// step 4

	interface Web3Context {
		customRpcMethods: CustomRpcMethodsPlugin;
	}
}
//highlight-end

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:::info After the plugin is ready, it is recommended to publish it on the NPM registry. :::

Step 5: Using the Web3 `CustomRPCPlugin` with a Web3 Instance

First add plugin in your plugin consumer project's package.json, create web3 and plugin instances, and after that use .registerPlugin method with some web3.js module (in following example its registered with main web3).

Once plugin is registered its custom methods will be available to use.

javascript

const { Web3 } = require('web3');
const CustomRpcMethodsPlugin = require('web3-plugin-example');

const web3 = new Web3('http://127.0.0.1:8545');

//highlight-start
web3.registerPlugin(new CustomRpcMethodsPlugin()); // step 5

web3.customRpcMethods.customRpcMethod(); //usage
//highlight-end

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typescript

import { Web3 } from 'web3';
import CustomRpcMethodsPlugin from 'web3-plugin-example';

const web3 = new Web3('http://127.0.0.1:8545');

//highlight-start
web3.registerPlugin(new CustomRpcMethodsPlugin()); // step 5

web3.customRpcMethods.customRpcMethod(); //usage
//highlight-end

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More Details of Plugin Feature

For more details follow :

Add custom RPC methods

Add custom RPC methods

Introduction

Creating new RPC methods Plugin in 4 Steps

Step 1: Setting Up Web3.js as a Peer Dependency and Creating a TypeScript Class

Step 2: Adding a Public pluginNamespace Property to the Plugin Class

Step 3: Creating Custom RPC Methods in the Plugin Class

Step 4: Enabling Access to the Plugin on the Web3 Object

Step 5: Using the Web3 CustomRPCPlugin with a Web3 Instance

More Details of Plugin Feature

Step 2: Adding a Public `pluginNamespace` Property to the Plugin Class

Step 5: Using the Web3 `CustomRPCPlugin` with a Web3 Instance