How to write a Node.js script to evaluate a transaction defined in the Invoke method of a chaincode?

Here is sample Node.js script, evaluate-transaction.js, that uses a given user identity from the local wallet to evaluate a transaction on chaincode.

/* Copyright (c) FYIcenter.com
 */
'use strict';
const { FileSystemWallet, Gateway } = require('fabric-network');
const fs = require('fs');
const ccp = JSON.parse(fs.readFileSync("connection.json", 'utf8'));

const user = process.argv[2];
const channel = process.argv[3];
const chaincode = process.argv[4];
const tx = process.argv.slice(5);

async function main() {
   try {

      // Create a new gateway for connecting to our peer node.
      const wallet = new FileSystemWallet("wallet");
      const gateway = new Gateway();
      await gateway.connect(ccp, { wallet, identity: user, discovery: { enabled: false } });

      // Get the network (channel) our contract is deployed to.
      const network = await gateway.getNetwork(channel);

      // Get the contract from the network.
      const contract = network.getContract(chaincode);

      // Evaluate the specified transaction.
      const result = await contract.evaluateTransaction(...tx);
      console.log("Tx function and arguments:");
      console.log(tx);
      console.log("Tx result: %s", result);

   } catch (error) {
      console.error(`Failed to evaluate transaction: ${error}`);
      process.exit(1);
   }
}

main();

To run this application script on your client system, you need finish the last tutorial to register "alice" to ca.example.com, and import the certificate and the key info the local wallet.

Try the script to call the queryAllCars() function of the "fabcar" Invoke() method.

$ node evaluate-transaction alice mychannel fabcar queryAllCars
Tx function and arguments:
[ 'queryAllCars' ]
Tx result: [
{"Key":"CAR0", "Record":{"colour":"blue","make":"Toyota","model":"Prius","owner":"Tomoko"}},
{"Key":"CAR1", "Record":{"colour":"red","make":"Ford","model":"Mustang","owner":"Brad"}},
{"Key":"CAR2", "Record":{"colour":"green","make":"Hyundai","model":"Tucson","owner":"Jin Soo"}},
...
]"

 

⇒ submit-transaction.js - Submit Chaincode Transaction

⇐ register-user.js - Register New User

⇑ Interfaces to Communicate with Ledger Peer

⇑⇑ Hyperledger Tutorials