Batch JSON-RPC requests

You can batch multiple JSON-RPC requests using MetaMask SDK.

The SDK's metamask_batch method enables you to batch multiple JSON-RPC requests in a single call, providing a streamlined approach for dapps to interact with EVM networks, and enabling complex sequences of actions. This method enhances performance, usability, and efficiency by reducing the number of network calls made to MetaMask.

Use cases include:

• Batching multiple signatures - Send multiple signing requests in one batch.

• Switching networks - Switch the EVM network, perform an action such as sending a transaction, and switch back, all in one batch.

• Mixed transactions and signatures - Combine transaction sending and signing requests in one batch.

metamask_batch opens up additional possibilities for sophisticated transaction flows in dapps, enhancing the user experience and operational efficiency.

Prerequisites

Set up MetaMask SDK in your JavaScript dapp.

Use the metamask_batch method

metamask_batch takes an array of JSON-RPC requests (ChainRPC[]) as its parameter.

Each request in the batch is independent. The user receives a prompt for each action within the batch, allowing them to approve or reject individual requests. If any request is rejected, the entire batch fails and an error is returned, ensuring integrity in transactional operations.

The method returns an array of results corresponding to each request.

React / Next.js / React Native example

The following is an example of using metamask_batch to batch personal_sign and eth_sendTransaction in React, Next.js, or React Native/Expo:

index.js

import { metamask_batch } from "metamask-sdk"

function MyComponent() {
  const handleBatchRequest = async () => {
    const batchRequests = [
      { method: "personal_sign", params: ["message", "address"] },
      {
        method: "eth_sendTransaction",
        params: [
          {
            /* Transaction parameters */
          },
        ],
      },
    ]

    try {
      const results = await metamask_batch(batchRequests)
      console.log(results) // Process results.
    } catch (error) {
      console.error("Batch request failed", error)
    }
  }

  return <button onClick={handleBatchRequest}>Send Batch Request</button>
}

Vue.js example

The following is an example of using metamask_batch to batch personal_sign and eth_sendTransaction in Vue.js:

App.vue

<script>
import { metamask_batch } from "metamask-sdk";

export default {
  methods: {
    async sendBatchRequest() {
      const batchRequests = [
        { method: "personal_sign", params: ["message", "address"] },
        {
          method: "eth_sendTransaction",
          params: [
            {
              /* Transaction parameters */
            },
          ],
        },
      ];

      try {
        const results = await metamask_batch(batchRequests);
        console.log(results);
      } catch (error) {
        console.error("Error in batch request", error);
      }
    }
  }
}
</script>

Best practices

Follow these guidelines when using metamask_batch:

• Ensure each request in the batch is properly formatted according to the JSON-RPC specifications.

• Handle errors appropriately, especially when a batch request is partially approved.

• Test batch operations to ensure consistent behavior across different networks and accounts.

• Be aware of the dependencies between chained requests. Avoid creating a dependency where the outcome of one request directly influences the context or validity of a subsequent request within the same batch. For example, avoid chaining a wallet_switchEthereumChain request with eth_signTypedData_v4, because eth_signTypedData_v4 relies on the current chain ID, which would be altered by wallet_switchEthereumChain. This approach ensures that each request in the batch operates independently and maintains its integrity, regardless of changes introduced by preceding requests in the batch.