Deep merge of JSON-like objects

merge.js

const merge = (() => {
  const duplicate = object => JSON.parse(JSON.stringify(object));
  return (...objects) => Object.assign(...objects.map(duplicate));
})();

// comparison with Object.assign

const foo = { a: [1] };
const bar = { b: [2] };

const merged = merge(foo, bar);
const assigned = Object.assign({}, foo, bar);

bar.b.push(3);

console.log(merged.b);   // => [2]
console.log(assigned.b); // => [2, 3]

Does this count as a JSON-like object?

const merged = merge({ a: { a1: true }}, { a: { a2: true }});

console.log(merged); // => { a: { a2: true }}

Wouldn't we want: { a: { a1: true, a2: true }}?

@cuth I think both results could be reasonable. I personally prefer the behavior of Object.assign (i.e. the last one wins) as it lets you easily override previous properties (useful for example when dealing with state objects).