Extending Web3.js

Although the preferred way to add custom RPC methods to Web3.js is to create a plugin, Web3.js also exposes a legacy extend method that can be used for the same purpose. Keep reading to learn how to use the legacy extend method to add a custom RPC method to an instance of Web3.js.

ExtensionObject

The legacy extend method accepts a single parameter that should implement the ExtensionObject interface. An ExtensionObject consists of two properties: an optional string property named property and a required property named methods that is an array of objects that implement the Method interface. The Method interface specifies two properties, both of which are required and both of which are strings: name and call. The property property of an Extension object can be used to specify the name of the Web3.js member property that will expose the custom RPC methods (if this parameter is omitted, the new RPC methods will be exposed by the "root" Web3.js object). Each element of the methods array from the ExtensionObject specifies a new custom RPC method - the name property is the name of the new function that will be used to call the custom RPC method and the call property is the actual RPC endpoint that should be invoked. The new function will accept parameters that will be passed along when invoking the RPC endpoint.

Here is a complete example of using the legacy extend method:

import { Web3 } from "web3";

const web3 = new Web3("https://eth.llamarpc.com");

async function main() {
  web3.extend({
    property: "BlockReceipts",
    methods: [
      {
        name: "getBlockReceipts",
        // https://www.quicknode.com/docs/ethereum/eth_getBlockReceipts
        call: "eth_getBlockReceipts",
      },
    ],
  });

  const receipts = await web3.BlockReceipts.getBlockReceipts("latest");
  console.log(receipts);
}

main();