Bun server fetching Ethereum address

README.md

To run this code:

1. Sign up with Chainstack.
2. Deploy a node.
3. View node access and credentials.

• Install Bun

• Run the code:

      bun --hot index.js

  The --hot flag uses a watcher feature to restart the server when changes are made.

index.js

const PORT = 5555;

Bun.serve({
  port: PORT,
  async fetch(request) {
    // Parse the request URL to get the pathname
    const urlObject = new URL(request.url);
    const pathname = urlObject.pathname;

    // Check if it's a GET request to the "/getBalance/" endpoint
    if (request.method === "GET" && pathname.startsWith("/getBalance/")) {
      try {
        const CHAINSTACK_NODE_URL = Bun.env.CHAINSTACK_NODE_URL;

        // Extract the address from the pathname
        const address = pathname.split("/getBalance/")[1];

        // Validate Ethereum address format (basic validation)
        if (!/^0x[a-fA-F0-9]{40}$/.test(address)) {
          return new Response(
            JSON.stringify({
              INVALID_ADDRESS_ERROR: "Invalid Ethereum address format",
            }),
            {
              status: 400,
              headers: { "Content-Type": "application/json" },
            }
          );
        }

        const response = await fetch(CHAINSTACK_NODE_URL, {
          method: "POST",
          headers: {
            "accept": "application/json",
            "content-type": "application/json",
          },
          body: JSON.stringify({
            id: 1,
            jsonrpc: "2.0",
            method: "eth_getBalance",
            params: [address, "latest"],
          }),
        });

        if (!response.ok) {
          throw new Error("Error fetching balance");
        }

        const data = await response.json();
        if (data.error) {
          throw new Error(
            data.error.message || "Error in Ethereum node response"
          );
        }

        let decimalValue = parseInt(data.result.substring(2), 16);
        let weiValue = BigInt(decimalValue);
        let divisor = BigInt("1000000000000000000");

        let wholeEthers = weiValue / divisor;
        let remainderWei = weiValue % divisor;

        let remainderEther = remainderWei.toString().padStart(18, "0");
        let etherValueWithDecimals = `${wholeEthers}.${remainderEther}`;

        return new Response(
          JSON.stringify({
            address: address,
            balance: etherValueWithDecimals,
            unit: "Ether",
          }),
          {
            status: 200,
            headers: { "Content-Type": "application/json" },
          }
        );
      } catch (error) {
        return new Response(`Error: ${error.message}`, { status: 500 });
      }
    }

    // Default response for other requests
    return new Response(
      JSON.stringify({
        error: "Endpoint does not exist",
      }),
      {
        status: 404, // HTTP status code for "Not Found"
        headers: { "Content-Type": "application/json" },
      }
    );
  },
});

console.log(`Bun server running on port ${PORT}...`);