'use strict';

function Transaction() {}

Transaction.start = (data) => {

console.log('\nstart transaction');

let delta = {};

const methods = {

commit: () => {

console.log('\ncommit transaction');

Object.assign(data, delta);

delta = {};

},

rollback: () => {

console.log('\nrollback transaction');

delta = {};

},

};

return new Proxy(data, {

get(target, key) {

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

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 };

const transaction = Transaction.start(data);

console.log('data', JSON.stringify(data));

console.log('transaction', JSON.stringify(transaction));

transaction.name = 'Mao Zedong';

transaction.born = 1893;

transaction.city = 'Shaoshan';

console.log('\noutput with JSON.stringify:');

console.log('data', JSON.stringify(data));

console.log('transaction', JSON.stringify(transaction));

console.log('\noutput with console.dir:');

console.dir({ transaction });

console.log('\noutput with for-in:');

for (const key in transaction) {

console.log(key, transaction[key]);

}

transaction.commit();

console.log('data', JSON.stringify(data));

console.log('transaction', JSON.stringify(transaction));