Javascript：如果对象具有匹配的键，如何用第二个对象的值替换第一个对象的值

Question

I have 2 js objects:

var date_dict = {2017_M1: 0, 2017_M10: 0, 2017_M11: 0}
var data_dict = {2017_M1: 10,  2017_M11: 50}

Expected output = {2017_M1: 10, 2017_M10: 0, 2017_M11: 50}

Aim: To map the values of data_dict (target) to date_dict (source) where they exist. Keep all keys of date_dict (source). Keep values of date_dict if not exist in data_dict.

There will never be any keys in data_dict that do not exist in date_dict (this is universe of dates).

I've tried, based on switching key/value an answer to How to replace object key with matching key value from another object

Below attempt just returns the date_dict, it doesn't get the data_dict values.

Thanks :

var expected_output = Object.fromEntries(
                Object.entries(date_dict).map(([k,v]) => [ k, (data_dict[v] || v)])

Answer 1

You can use the spread operator for this:

const expected_output = {
  ...date_dict,
  ...data_dict
};