example.js

const { jsonToEth, ethToJson } = require ('./utils');
const Web3 = require('web3');
const fs = require('fs');
const crypto = require('crypto');

// Smart contracts should be deployed beforehand with 'truffle migrate'
async function processJsonExample (jsonData) {
  const artifacts = JSON.parse(fs.readFileSync('./contracts/build/Storage.json'));

// Ganache network
  const web3 = new Web3('http://127.0.0.1:7545');
  const storage = new web3.eth.Contract(artifacts.abi, artifacts.networks['5777'].address);

  const address = (await web3.eth.getAccounts())[0];
  const id = '0x' + crypto.randomBytes(32).toString('hex');

  await storage.methods.set(id, ...jsonToEth(jsonData), address)
    .send({ from: address, gas: 1000000 }).catch(error => console.log(error.message));

  let keyName = Web3.utils.stringToHex('keyToChange');
  let keyValue = Web3.utils.stringToHex('changed !');
  await storage.methods.setByDataKey(id, keyName, keyValue)
    .send({ from: address, gas: 1000000 }).catch(error => console.log(error.message));

  keyName = Web3.utils.stringToHex('keyToDelete');
  await storage.methods.removeByDataKey(id, keyName)
    .send({ from: address, gas: 1000000 }).catch(error => console.log(error.message));

  keyName = Web3.utils.stringToHex('newKey');
  keyValue = Web3.utils.stringToHex('I am a value of new key !');
  await storage.methods.setByDataKey(id, keyName, keyValue)
    .send({ from: address, gas: 1000000 }).catch(error => console.log(error.message));

  const ethDataFromContract = await storage.methods.get(id).call();
  return ethToJson(ethDataFromContract);
}

const jsonData = JSON.stringify({
  keyToChange: 'change me !',
  keyNotToTouch: 'do not touch me !',
  keyToDelete: 'delete me !',
});

processJsonExample(jsonData)
  .then(value => console.log(`Initial JSON value: ${jsonData}, JSON value after processing in Smart Contract: ${value}`));