'use strict';

const start = (data) => {

console.log('\nstart transaction');

let delta = {};

const commit = () => {

console.log('\ncommit transaction');

Object.assign(data, delta);

delta = {};

};

return new Proxy(data, {

get(target, key) {

if (key === 'commit') return commit;

if (Object.hasOwn(delta, key)) return delta[key];

return target[key];

},

set(target, key, val) {

console.log('set', key, val);

if (target[key] === val) delete delta[key];

else delta[key] = val;

return true;

},

});

};

// Usage

const data = { name: 'Marcus Aurelius', born: 121 };

console.log('data.name', data.name);

console.log('data.born', data.born);

const transaction = start(data);

transaction.name = 'Mao Zedong';

transaction.born = 1893;

console.log('data.name', data.name);

console.log('data.born', data.born);

console.log('transaction.name', transaction.name);

console.log('transaction.born', transaction.born);

transaction.commit();

console.log('data.name', data.name);

console.log('data.born', data.born);

console.log('transaction.name', transaction.name);

console.log('transaction.born', transaction.born);